Tag Archives: temperature

How hot is the sun?

The Sun is a ball of nuclear plasma so large its own weight keeps it from exploding. Very cool, but also quite hot. However, the Sun has a complicated interior structure, and surprisingly large temperature variations, both on and under its surface. Today, we’re going to look at why this is, and how we know.

A ‘Pumpkin Sun’ composite image created by NASA in 2014. Colored gold-yellow, with active regions being brighter for “a particularly Halloween-like appearance”. Image credits NASA.

A lot of the things happening on Earth are, ultimately, fueled by energy from the Sun. We see that energy as sunshine, feel it hot on our skin on a clear day. It drives winds, and it powers rain cycles. Almost all life on Earth is fed by plants capturing sunlight. It’s very fortunate for us, then, that the Sun produces a monumental amount of energy. Just a fraction of its output reaches our planet, since a lot of it is lost in transit, reflected, or radiates away from Earth and into the void. Even so, it’s much more than we’d know what to do with, and only about 1% of it is enough to keep all the plants on Earth alive.

Energy is never lost or created, but transformed from one ‘flavor’ into another. Still, not all of them are equal, and heat seems to be the baseline that all others eventually degrade into. The Sun, therefore, gets quite hot.

Just how hot?

It depends on a lot of factors — mostly on exactly where you’re taking the measurement. There’s a lot of variation here.

First off is the Sun’s core. Here is where the fusion reaction that drives the star actually takes place. Due to the sheer mass of gas pressing down on the core, ambient pressure here is immense. Temperatures, too, are extremely high, due to how compressed everything gets. This is ideal, because such extreme conditions are needed for fusion to take place. To the best of our knowledge, temperatures at the core of the Sun can reach in excess of 15 million °C (27 million °F), which is a lot.

Image credits NASA, edited for clarity.

The next layer of the star is its ‘radiative zone’. Energy from the core moves out to this area, carried by bodies of superheated, ionized atoms, where it becomes trapped. It spends up to 1 million years here, before finally managing to escape the strong gravity and electromagnetic fields and reach the convective zone. This zone represents the upper layer of the Sun’s core, and temperatures here are believed to be around 2 million °C (3.5 million °F).

Hot plasma from this convective zone can bubble up towards the surface of the Sun. The next layer it encounters is the photosphere, which is about 5,500 °C (10,000 °F), significantly cooler compared to the previous layer. It is here that the radiation produced inside the star can first be perceived as light by an outside observer. A photosphere (‘sphere of light’ in ancient Greek) is defined as the deepest region of a light-emitting body that is still transparent to photons of certain wavelengths. In other words, the photosphere starts where the Sun’s plasma becomes transparent enough for light to be able to escape it.

However, the photosphere is not uniform. Areas of intense electromagnetic activity produce sunspots, which are darker and cooler than their surroundings; temperatures in the center of a sunspot can drop to lows of 4,000 °C (7,300 °F).

The next layer, the chromosphere (‘sphere of colors’ in ancient Greek), is a tad cooler, at about 4,320 °C (7,800 °F) on average. Light from this layer is thus dimmer, and we don’t usually see it. But, during a solar eclipse (when the moon covers the sun), this is the really fancy bit you see around its outline, the red rim surrounding the Sun. This color is emitted by the high content of hydrogen gas in the chromosphere.

In relative terms, temperatures in the photo- and chromatosphere aren’t that high — a candle, for example, burns at around 1,000 °C (1,800 °F). We know these two layers exist because their relatively mellow conditions allow for simple molecules such as water and carbon monoxide to survive, and we’ve picked up on their spectral emissions.

Lastly, there is the corona — the Sun’s crown. A bit unexpectedly, temperatures shoot back up in this layer, despite it being the farthest away from the core. In fact, it has average temperatures at the same order of magnitude as the core, although they are still lower. These range between 1 million °C and 10 million °C (roughly 1.7 – 17 million °F), according to the National Solar Observatory (NSO). The corona and chromatosphere are kept separated from this layer by a transition zone of highly-ionized helium atoms. This is less of a hard boundary and more of a chaotic, ever-churning sea of clouds. The corona might be so hot due to ‘nanoflares‘, but we’re still unsure.

Beyond the corona lies the Sun’s extended atmosphere, the heliosphere, which is less of a layer per se and more of an area of influence that the Sun exerts. While emissions such as solar winds or flares can send super-heated, charged particles flying off from a star into its heliosphere, this is much cooler than the layers we’ve discussed previously. The main component of the heliosphere is magnetic, and it has a key part to play in forming the Sun’s shield around our solar system.

How do we know how hot it is?

False-color 3-layer composite from the TRACE satellite, showing the solar corona for a “moderately active Sun”. Red indicates regions with high temperatures and activity, blue and green for colder areas. Loops can be seen connecting the active areas. Image credits NASA via Wikimedia.

Sticking a thermometer in the Sun is, understandably, a bit tricky. So we’ve had to rely on indirect methods of measurement to tell exactly how hot it can become.

If you put a kettle on to boil, you’ll be able to feel heat coming from the water even after you take it off the stove. How much of it you will perceive depends a lot on how close you hold your hand to the water. This process relies on the radiative properties of electromagnetic energy. To keep it simple, particles start moving when they heat up, and this motion generates thermal radiation; infrared cameras pick up on this kind of radiation, for example. Our senses perceive it as heat.

One of the simplest and also least accurate ways of assessing the Sun’s temperature is our own senses. Sunlight can be really hot on a clear day. Considering the star is around 149 million kilometers away, it must be outputting a lot of thermal energy for it to reach all the way here. Still, researchers like numbers, especially accurate ones, so they did develop several other means of gauging the star’s temperature.

One approach uses the link between heat and the light coming from a body — because in physics, unlike life, being hotter automatically makes you brighter, too.

Thermal radiation is a kind of electromagnetic radiation, but so is light. In very broad terms, as long as the cause is temperature, the brighter an object glows, the hotter it is. Irons heating in a forge are a good example. The hue can help us determine this temperature exactly. Red light is cooler than yellow light which is cooler than blue, and so on. A yellow-flamed candle burns colder than the blue flames on your stove.

A series of photographs of the Sun taken roughly at the same time, showcasing how different wavelength intervals can carry more or less energy. The first on the left is filtered white (normal) light. Image credits NASA / GSFC / Solar Dynamics Observatory.

That’s the working principle. In practice it becomes more complicated since the Sun doesn’t output a single type (wavelength) of light, but a whole cocktail of wavelengths that mix and interact to create the final, white light we perceive. We use a device called a spectrograph to tease these colors apart into individual wavelengths. They work much like raindrops do when creating rainbows.

Once we break down sunlight like this, we can look at each individual color (wavelength) of light and determine what temperature is associated with it. Every wavelength carries different amounts of energy, so the final step is to average out their temperatures to determine the final ‘product’. Think of it like determining the energy level of the middle-most color by looking at each individual color present in sunlight.

Sunlight can also be used to determine the chemical composition of our star. Every stellar body emits light across multiple wavelengths. But these ’emission spectra’ also show very small, generally well-defined gaps, tight wavelength intervals where no light is emitted (or where light is being absorbed). This comes down to how atoms interact with radiation but, suffice to say, these gaps are extremely reliable signatures of certain elements. As long as you understand the trace each of them leaves on the emission spectrum, you can determine a body’s composition from the light it emits. We call these traces Fraunhofer lines.

Which extinction lines are present, as well as how well-defined they are, are influenced by temperature. As such, this step can help determine both the composition and temperature of a star.

Still, we said earlier that the photosphere is a hard boundary in regards to our perception of light — we can’t see below this limit. Spectroscopy, then, as well as other optical methods, can only help us determine temperatures down to this layer. At the same time, even if the corona is much hotter, it’s also significantly less bright than the photosphere, so it has a very small contribution to this type of measurement.

As for anything deeper than the photosphere? That’s more theoretical. It’s not pulled out of our assumptions, but it’s still a theoretical estimate. Temperature conditions inside the Sun are based on the idea that it is in a state of hydrostatic equilibrium. That is, that its gravity (inward pressure) and expansive (outward pressure) generated by nuclear fusion at the core cancel each other out. If they wouldn’t, the star would blow up or turn black holey, so it’s a solid starting point.

If you combine this with chemical readings from spectroscopy, and estimates of the star’s mass (also calculated or obtained indirectly), you can determine what temperatures should be at the core to keep it all stable. We also know from our efforts at making fusion happen on Earth that humongous pressures and temperatures are needed to convince hydrogen atoms to merge; the Sun does that on a monumental scale, every second.

This is all based on tried-tested-and-true methods and theorems regarding natural processes, so they are reliable, but they’re still just estimates. If you’re the kind of person that needs exact measurements and figures, talking about the Sun might not be the best hobby for you. But, if it makes you find a way to go there and actually stick a thermometer in the thing so we can all find out, I won’t complain.

2020? Yeah, that’s the hottest year on record (tied with 2016)

The climate crisis did not take a break last year. The year 2020 is tiedwith 2016 as the hottest year on record, according to European climate researchers. The record warmth fueled record wildfires in the Arctic, a large number of tropical storms in the Atlantic, and deadly heatwaves.

Air temperature at a height of two metres for 2020, shown relative to its 1981–2010 average. Image credit: Copernicus

Although emissions dropped 7% last year due to the lockdowns, they continued to build up in the atmosphere and thanks to inertia from previous years, we ended up with a new record. The average surface temperature was 1.25ºC higher than in the pre-industrial period of 1850-1900, dangerously close to the 1.5ºC target set in the Paris Agreement, which is already looking more and more unlikely.

Only 2016 matched the heat seen in 2020, but that year had a natural El Niño climate event that boosts temperatures. Without it, 2020 would have almost certainly been the hottest year so far. Scientists have repeatedly warned that urgent action is needed for the world to avoid the worst consequences of the climate crisis.

The data was published by the European Union’s Copernicus Climate Change Service (C3S), which showed that the past six years were the hottest six on record and that 2011-2020 was the warmest decade recorded. CO2 concentrations in the atmosphere rose at a rate of approximately 2.3 ppm/year, reaching a maximum of 413 ppm during May.

Vincent-Henri Peuch, Director of the Copernicus Atmosphere Monitoring Service (CAMS), said in a statement: “While carbon dioxide concentrations have risen slightly less in 2020 than in 2019, this is no cause for complacency. Until the net global emissions reduce to zero, CO2 will continue to accumulate in the atmosphere and drive further climate change.”

For Europe, 2020 was the hottest year on record, 1.6ºC above the long-term average. Seasonally winter 2019/20 and autumn 2020 were also the warmest recorded. Winter 2020, from December 2019 to February 2020, exceeded the previous warmest of 2016 by almost 1.4°C, while autumn (September to November 2020) passed the old record set in 2006 by 0.4°C

The Arctic is experiencing faster global warming than the rest of the planet, a trend that was also reflected in the 2020 numbers. A large part of it saw annual average temperatures more than 6ºC higher than a baseline average from 1981 to 2010. On a monthly basis, the largest positive temperature anomalies reached more than 8°C.

Decadal averages of global air temperature at a height of two metres estimated change since the pre-industrial period according to different datasets. Image credit: Copernicus.

This led to extensive wildfires across the Arctic (yes, wildfires in the Arctic), with the first detected in May, continuing throughout summer and well into autumn. As a result, poleward of the Arctic Circle, fires released a record amount of 244 megatons of CO2 in 2020, over a third more than the 2019 record. During the second half of the year, Arctic sea ice was significantly lower than average for the time of the year.

The Northern Hemisphere had above-average temperatures for the year, apart from a region over the central North Atlantic. In contrast, parts of the Southern Hemisphere saw below-average temperatures, especially over the eastern equatorial Pacific, associated with the cooler La Niña conditions developing during the second half of the year.

“The extraordinary climate events of 2020 and the data from the Copernicus Climate Change Service show us that we have no time to lose. We must come together as a global community, to ensure a just transition to a net-zero future. It will be difficult, but the cost of inaction is too great,” said Matthias Petschke, Director for Space, European Commission’s Directorate-General for Defence industry and Space, in a statement.

There’s no way around it: unless we see drastic and quick reductions in global emissions, years will get hotter and hotter and we — along with everyone else on Earth — will pay the price.

In 10 to 20 years, it will be so hot that tropical trees live shorter lives

It’s not the best time to be a tropical tree, as rising average temperatures risk impacting their lifespan.

Image credits Roel Brienen.

A new study explains that the longevity of trees at the tropics is shortened by higher temperatures. The findings help further our understanding of how climate change will impact ecosystems in the area and its effects on the rest of the planet. The team argues this is the first direct evidence that tropical trees experience shorter lives in hotter environments, and that forests all around the world will be affected.


“Many regions in the tropics are heating up particularly rapidly and substantial areas will become warmer, on average, than approximately 25 °C,” says Professor Manuel Gloor at the University of Leeds, a co-author of the paper.

“Our findings – which are the first to demonstrate that there is a temperature threshold – suggests that for trees in these regions, their longevity is likely to be negatively affected.”

The temperature above which trees become affected is 25 °C, the paper explains. This result is based on four years’ worth of tree ring data recovered worldwide. Roughly 100,000 trees from 400 species in 3,000 sites across the planet formed the dataset. All in all, the team reports that although tropical trees grow twice as fast as those in cold areas, they also live shorter lives (186 years vs 322 years on average).

Average temperatures in tropical forests today sit between 21 °C and 30 °C depending on location. These averages will rise alongside the rest of the world to around 2.5 °C above pre-industrial levels over the next 10 to 20 years. The effect this will have on trees varies depending on exactly how much hotter it gets. Changes in precipitation patterns (another effect of climate change) are going to exacerbate this ever further.

Substantial areas of today’s rainforests will see significantly lower tree longevity. They only cover 7% of the Earth’s surface, but harbor around 50% of its species of plants and animals, and a corresponding 50% of the planet’s carbon stocks. Any change here will have strong, global echoes for habitats, air quality, and carbon scrubbing ability.

“These results are a warning sign that, along with deforestation, global warming adds extra stress on the Earth’s tropical forests,” says Dr Roel Brienen from Leeds, paper co-author.

“If tropical trees die earlier, this will affect how much carbon these forests can hold, raising concerns about the future potential of forests to offset CO2 emissions from fossil fuel burning. It could also cause changes in biodiversity and a decrease in the number of species on the planet.”

Tropical forests in South America are closest to this threshold, but they’re not the only ones at risk. Even the Congo Forest in west Africa, the world’s second largest but with lower average temperatures, will be affected.

The saddest finding here, in the words of co-author Marcos Buckeridge, Director of the Biosciences Institute of the University of São Paulo, is that it’s “unavoidable”. It’s too late to stop average temperatures from passing this threshold “even if we were to take drastic emissions reductions measures”.

The paper “Global tree-ring analysis reveals rapid decrease in tropical tree longevity with temperature” has been published in the journal Proceedings of the National Academy of Sciences.

This smart ring detects fever (and possibly COVID-19) before you feel it

Oura ring monitors a range of signals, including continuous temperature, heart rate, respiration rate and activity.  The product is not FDA registered. Credit: Oura Ring.

Since fever is one of the main symptoms of COVID-19, in many countries temperature checkups are required to enter public indoor premises such as a mall or airport. But these spot checks “are the equivalent of catching a syllable per minute in a conversation, rather than whole sentences,” said Benjamin Smarr, a professor of bioengineering at the University of California San Diego, who thought of a better alternative driven by many more data points.

In a new study, Smarr and colleagues have presented the findings of a trial involving 65,000 people who have worn the Oura smart ring. The wearable device developed by a Finnish startup (also Oura) records temperature, heart rate, respiratory rate, and levels of physical activity. Among the participants, 50 had COVD-19, and scientists say that these infections can be predicted from the ring’s data.

“With wearable devices that can measure temperature, we can begin to envision a public COVID early alert system,” Smarr said in a statement.

Unlike a random temperature spot check, the Oura ring gathers information around the clock, day and night, over long periods of time. This wealth of data allowed the researchers to notice that fever appeared before the participants were reporting symptoms, as well as among those that never reported symptoms. For 38 of the 50 participants, fever was identified when symptoms were unreported or even unnoticed.

Previously, some public health experts have suggested that some cases of fever, and consequently potentially of COVID-19, may go underreported or unnoticed, separate from truly asymptomatic cases. “Wearables, therefore, may contribute to identifying rates of asymptomatic [illness] as opposed to unreported illness, [which is] of special importance in the COVID-19 pandemic,” the authors noted in their study published in the journal Scientific Reports.

The researchers claim that the participants’ data had not been violated during the study’s timeframe. The data was stripped of personal information, including the location data, and each subject is known by a random ID number. The 50 participants had contracted COVID-19 before joining the study but had been wearing Oura rings during the time they fell ill. They provided symptom summaries and granted researchers full access to their rings’ data.

Data collected by the ring will be processed by an algorithm that may reveal symptom outset before a patient actually feels the symptoms. Credit: University of California San Diego.

This is how the researchers noticed that temperature signals corresponding to fever among those sick with COVID-19 were very obvious. In fact, the chart tracking people who had a fever looked like it was on fire, Smarr said.

While the sample size of this study is too small to draw conclusions for the general population, the authors claim that their study raises some important questions. How many so-called asymptomatic cases are truly asymptomatic, for instance? How many might just be unnoticed or underreported?

“If wearables allow us to detect COVID-19 early, people can begin physical isolation practices and obtain testing so as to reduce the spread of the virus,” Ashley Mason, a professor in the Department of Psychiatry and the Osher Center for Integrative Medicine at UC San Francisco, said in a statement. “In this way, an ounce of prevention may be worth even more than a pound of cure.”

The researchers are currently working on an algorithm that can predict the onset of symptoms such as fever, cough, and fatigue. They hope to have it ready by the end of the year.

Can weather help against the coronavirus? New study says ‘no, but behavior can’

New research reports that temperature and humidity do not play a significant role in the spread of the coronavirus. The study was led by members from The University of Texas at Austin.

Image credits Ina Hoekstra.

The authors aimed to better understand how temperatures influence the spread of the coronavirus. At the onset of the pandemic, it was hoped that the hot summer days would reduce its spread. The findings now, however, suggest that neither temperatures nor humidity play any significant role in the virus’ activity — its spread depends almost entirely on human behavior.

However, temperatures do have an influence on how people act, the team notes, so it can indirectly influence the spread.

All-weather bug

“The effect of weather is low and other features such as mobility have more impact than weather,” said team leader Dev Niyogi, a professor at UT Austin’s Jackson School of Geosciences and Cockrell School of Engineering. “In terms of relative importance, weather is one of the last parameters.”

The team lumped temperature and humidity together to form a single value, the “equivalent air temperature”. They then analyzed how variations in this value influenced the spread of the virus in different areas of the US and elsewhere between March and July of 2020. They also looked at the relationship between human behavior and coronavirus spread using cellphone data on a countrywide and statewide scale.

Across scales, they found that weather had nearly no influence on the spread of the virus. Compared to other factors, from a statistical point of view, weather had an influence (‘relative importance’) over the virus’ spread of less than 3%, the team reports, and they found no reason to believe that any type of weather was more conducive to infections than any other.

On the other hand, human behavior had an especially high influence. Taking a trip or spending time away from home were the two single largest contributing factors to COVID-19 spread, having a relative importance of around 34% and 26% respectively. Next were population and urban density, with a relative importance of about 23% and 13% respectively.

“We shouldn’t think of the problem as something driven by weather and climate,” Jamshidi said. “We should take personal precautions, be aware of the factors in urban exposure.”

Previous assumptions on the effect of weather on the virus were largely based on studies carried out in a laboratory setting or on related viruses, which may have skewed the results, according to the author.

Baniasad, a biochemist and pharmacist, said that assumptions about how coronavirus would respond with weather are largely informed by studies conducted in laboratory settings on related viruses. She said that this study illustrates the importance of studies that analyze how the coronavirus spreads through human communities.

“When you study something in a lab, it’s a supervised environment. It’s hard to scale up to society,” said Maryam Baniasad, a doctoral candidate at Ohio State University and co-author of the paper. “This was our first motivation to do a more broad study.”

One of the main lessons we should derive from the pandemic and this study is that we need to analyze phenomena on a “human scale” — the scale at which humans live their day-to-day lives — in order to properly understand them, says Niyogi.

“COVID, it is claimed, could change everything,” Niyogi said. “We have been looking at weather and climate outlooks as a system that we scale down, down, down and then seeing how it might affect humans. Now, we are flipping the case and upscaling, starting at human exposure scale and then going outwards. This is a new paradigm we will need for studying virus exposure and human environmental modeling systems involving new sensing and AI-like techniques.”

The paper “Global to USA County Scale Analysis of Weather, Urban Density, Mobility, Homestay, and Mask Use on COVID-19” has been published in the International Journal of Environmental Research and Public Health.

Temperatures in Death Valley hit 130 degrees, possibly the highest temperature on Earth

As the US west coast is dealing with a heatwave, the temperatures at Death Valley National Park in California reached 130 Fahrenheit (54.4ºC) on Sunday, possibly breaking the record for the highest temperature ever (reliably) recorded on Earth.

Credit Flickr Sandrine Neel (CC BY 2.0)

The reading, obtained at 3:41 PM, is now being verified by the United States Weather Service, although climate experts are confident it will be confirmed. It would not only be the hottest temperature recorded in the US since 1913, but also break the world’s temperature record.

“Everything I’ve seen so far indicates that is a legitimate observation,” Randy Cerveny, who leads the World Meteorological Organization’s weather and climate extremes team, told The Washington Post. “I am recommending that the World Meteorological Organization preliminarily accept the observation.”

The current record for the hottest temperature on Earth is also held by Death Valley, at 134 Fahrenheit (56.6ºC), recorded on July 10, 1913. But the measurement is disputed and considered erroneous by modern weather experts.

Christopher Burt, an expert on extreme weather data, concluded in a study in 2016 that it was “essentially not possible from a meteorological perspective” as the Death Valley reading doesn’t agree with the temperatures in the region as a whole.

Credit National Weather Service

A record-high temperature for Africa was registered in Tunisia at 131 Fahrenheit (55ºC) but, according to Burt, that reading, as well as others in Africa from the colonial period, have “serious credibility issues.”

That’s why experts claim that the hottest temperature ever “reliably” registered on Earth was experienced in 2013 at Death Valley, with a temperature of 129.2 Fahrenheit (54ºC). That is, until now, as the recent reading could mark a new record for the planet.

Death Valley is the hottest, driest, and lowest location in the US. The temperature was measured at Furnace Creek, which is 190 feet below sea level in the Mojave Desert in California. It’s well-known for its high temperatures, especially in July. In 2018, during that month, temperatures reached 120 Fahrenheit (48.8ºC) on 21 different days.

Soaring heat

The temperature was recorded during a heatwave that stretches from Arizona in the south-west up the coast to Washington State in the north-west. It should peak on Tuesday before temperatures start dropping later in the week. Nevertheless, the heat will continue for at least 10 more days.

Oakland, California, broke a local record on Friday by reaching 100 Fahrenheit (37.7ºC) for the first time, while Phoenix had its highest temperature for the month at 117 Fahrenheit (47.2ºC). Then on Saturday, Needles, California had its highest temperature on record for August at 123 Fahrenheit (50.5ºC).

The heatwave led to the growing use of electricity for air conditioning, causing problems with the power grid. California’s Independent System Operator (CISO), which controls the state’s power, declared a Stage 3 Emergency, meaning that “demand [for electricity] begins to outpace supply.”

Climate scientists agree that the duration, frequency, and intensity of heatwaves worldwide is increasing due to human-caused climate change. Daily record temperatures over the past decade have set twice as often as record lows across the continental United States, with heat waves becoming more frequent especially in the West.

The hottest planet in the solar system — and why it’s probably not what you think

When it comes to the surface temperature of planets, distance to the Sun is the main factor, but it’s not the only one. Turns out, the atmosphere (and in some cases geological processes) can have a major impact.

This is why the hottest planet in the solar system isn’t Mercury (the closest to the Sun), but Venus — and the reason has to do with something we’re very familiar with: carbon dioxide.

Venus, in its terrifying glory. Image credits: NASA / JPL.

A familiar culprit: greenhouse gas

Venus, named after the Roman goddess of Love (Aphrodite for the Greeks), is not exactly an inviting place. Its scorching surface can reach 880°F (471°C), and if that doesn’t scare you, Venus is riddled with active volcanoes and hot, toxic sulfur fumes.

It’s no surprise that Venus is hot since it’s much closer to the Sun than the Earth. Venus lies 108.93 million km away from the Sun, 30% closer than the Earth. But why is Venus hotter than Mercury, which lies only 59.187 million km from the Sun?

The answer lies in the Venusian atmosphere.

Image credit: Johns Hopkins University Applied Physics Laboratory.

The atmospheric pressure on Venus is 92 times stronger than that of Earth — it would feel like being 900 m (3,000 ft) underwater. This thick atmosphere wraps the planet like a blanket, and to make matters even hotter, the atmosphere is 96% carbon dioxide — which, as you’re probably aware, is an important greenhouse gas and a driver of rising temperatures. In other words, Venus has a runaway greenhouse gas problem that traps heat in the atmosphere.

Meanwhile, Mercury has a very thin atmosphere. Much of the heat that Mercury receives from the sun is quickly lost back into space, whereas heat on Venus doesn’t escape.

It’s a never-ending cycle of heat being trapped inside by carbon dioxide and releasing more carbon dioxide. This is what happens when an atmosphere absorbs too much carbon dioxide: the heat has nowhere to go and it triggers a self-enforcing feedback loop.

This becomes even more obvious when we look at the difference between the maximum temperature and the average temperature.

The day is longer than the year

The hellish environment on Venus — a false-color reconstruction from radar data depicting an impact crater. Image credits: NASA.

Both Mercury and Venus rotate very slowly; on Venus, a day lasts 243 Earth days, while a year lasts 225 Earth days — the Venusian day is longer than the year.

Because they rotate so slowly, you’d expect the planets to have massive temperature differences between the sunny side and the dark side — and that’s exactly what we see on Mercury. There’s a huge, over 1000 °F difference between day and night. But for Venus, that’s not really the case.

Because Venus has such a thick and greenhouse-potent atmosphere, the temperature is relatively constant on the entire planet. While the hottest temperature on Mercury is close to that of Venus, if we we were to take an average, it wouldn’t even be close.

Planet / SatelliteMinimum surface TemperatureMaximum Surface Temperature
Mercury-275 °F (- 170°C) 840 °F (449°C)
Venus870 °F (465°C)870 °F (465°C)
Earth– 129 °F (- 89°C)136 °F (58°C)
Moon– 280 °F (- 173°C)260 °F (127°C)
Mars– 195 °F (- 125°C)70 °F (20°C)

If Venus didn’t have the atmosphere it does, its night temperature would also be much lower, like Mercury’s — and the average temperature would also be lower than Mercury’s.

Another consequence of this atmosphere is that there’s no ice on Venus, which is hardly surprising given the average temperature. While on Mercury, ice can find shelter in the polar, always-shaded impact craters where temperatures are below freezing. NASA’s MESSENGER mission detected evidence of water ice at both of Mercury’s poles, probably delivered by comet impacts.

Meanwhile, the surface of Venus is extremely dry.

Earth’s twin?

It’s not always clear if the planet was always like this. During its early evolution, Venus likely had liquid water on its surface, but it was ultimately evaporated by ultraviolet rays from the Sun. If, through some magical experiment, you were to create some water on Venus, it would boil away almost immediately. Yet despite all these differences, Venus was once considered Earth’s twin.

Here’s one of the few photos from the surface of Venus, courtesy of the Venera 13 mission.

The reason for this is mostly regarding the planet’s size and mass. Venus and Earth, two neighboring planets, are very similar in some regards: Earth has a mean radius of 6,371 km, while Venus has a radius of about 6,052 km. Meanwhile, the mass of the Earth is 5,972,370,000 quadrillion kg, compared to 4,867,500,000 quadrillion kg for Venus. So essentially, Venus is 0.9499 the size of Earth and 0.815 the mass. It also has an atmosphere… and that’s pretty much where the similarities end.

Around 60% of Venus is covered by flat, smooth plains, marred by thousands of active volcanoes, ranging from 0.5 to 150 miles (0.8 to 240 km) wide. Venus features long, winding canals that run for more than 3,000 miles (5,000 km) — longer than any other planet.

The temperature is ungodly, as we’ve already mentioned, the atmosphere is thick and heavy, permanently covered in clouds. Most man-made materials would melt rapidly on Venus, and a human mission to Venus is nothing more than a pipe dream at this point.

Venus also rotates in the opposite direction than the Earth, and as we mentioned previously, it rotates very slowly.

If Venus is Earth’s twin, it can only qualify as its evil twin.

How we study Venus

Up until the 1960s, there was rich speculation that Venus may harbor life forms — but all that dwindled quickly when spacecraft actually started studying Venus.

Studying Venus is no easy feat. In fact, Venus is so inhospitable that many scientists were skeptical that a mission would even be possible. The Soviets sent a few missions to Venus, but the first ones all failed.

Mariner 2 was the first spacecraft to visit Venus in 1962. Eventually, in 1981, the Venera 13 mission finally managed to make it through the hot layers of the atmosphere and land on the surface. It managed to survive for 127 minutes, during which it sent color photos and measurements to Earth.

Then, transmission stopped and Venera 13 melted.

Image from the Venera 13 lander.

In 1990, the US spacecraft Magellan used radars to map the Venusian surface — an extremely important step, since Venus is always shrouded by sulfur layers that make it impossible for visible light to pass. Magellan mapped 98% of the surface with a resolution of approximately 100 meters and are still the most detailed maps we have of Venus. In more recent times, interest in Venus has decreased and recent missions have only been flybys, taking snapshots of Venus en route to other destinations. The Japanese mission Akatsuki, plagued by problems, is currently studying Venus’ atmosphere.

A three-dimensional perspective view acquired by the Magellan probe. Image credits: NASA.

Understanding the atmosphere and atmospheric processes on Venus could help us better understand some of the atmospheric phenomena we see here on Earth.

Venus’ runaway greenhouse effect could show us how the Earth might look in the future if we don’t take climate change seriously. It’s an important lesson on what can happen when a planet has a high carbon dioxide level in the atmosphere. According to recent studies, Venus may have had a liquid ocean and a habitable surface for up to 2 billion years of its early history — an important cautionary tale.

Lastly, although Venus is hellish and inhospitable, some researchers still believe that extremophiles (organisms adapted to extreme conditions) could still survive on Venus. In 2019, researchers proposed that an unexplained absorption phenomenon could be explained by colonies of microbes in the atmosphere on Venus. While far from being a promising place to look for life, it’s still intriguing enough to study.

Venus studies have been great lessons, enabling researchers to better understand other rocky planets, as well as the Earth.

It’s a hot, hellish place — the hottest planet in the solar system. But we can still learn from it.

What is temperature and what does it truly measure?

Credit: Pixabay.

Everybody has used a thermometer at least once in their lives, but even without one, our bodies are decent sensors for measuring how hot or cold things are upon contact. We refer to this property as temperature which, in more technical terms, represents the average kinetic energy of the atoms and molecules comprising an object.

Heat or temperature?

Before we go any further with our discussion, it’s important to get something out of the way.

Often heat and temperature are used interchangeably — this is wrong. While the two concepts are related, temperature is distinct from heat.

Temperature describes the internet energy of a system, whereas heat refers to the energy transferred between two objects at different temperatures.

But, as you might have noticed, heat can be very useful when describing temperature.

Imagine a hot cup of coffee. Before pouring the hot elixir of life, the cup had the same temperature as the air surrounding it. However, once it came in contact with the liquid, heat was transferred, increasing its temperature. Now, if you touch the cup, you can feel that it’s hot.

But, given enough time, both the cup and its contents will reach thermal equilibrium with the ambient air. Essentially, they all have the same temperature, which is another way of saying there is no longer a net transfer of energy. Physicists call this the “zeroth law of thermodynamics”. By this principle, heat can only flow from a body that has a higher temperature than another body with which it is in contact — and never the other way around.

The dance of molecules

Everything in this universe is in motion, and motion begets kinetic energy. The faster a particle is moving, the more kinetic energy it has. In fact, kinetic energy increases exponentially with particle velocity.

Where does temperature fit into all of this? Well, temperature is simply an average measure of the kinetic energy for particles of matter. Another way of putting it would be that temperature simply describes the average vibration of particles.

Because the motion of all particles is random, they don’t all move at the same speed and in the same direction. Some bump into each other and transfer momentum, further increasing their motion. For this reason, not all particles that comprise an object will have the same kinetic energy.

In other words, when we measure an object’s temperature, we actually measure the average kinetic energy of all the particles in the object. However, it’s just an approximation.

Within this line of reasoning, the higher the temperature, the higher the motion of the particles. Conversely, when the temperature drops, the motion of the particles is slower. For instance, dyes spread faster through hot water than cold water.

This is why at a temperature of absolute zero, the motion of particles grinds to a halt. Absolute zero is just a theoretical construct and, in practice, it can never be achieved. However, physicists have been able to cool things to a fraction of a degree above zero, trapping atoms and molecules, or creating exotic phases of matter such as the Bose-Einstein condensate (BEC).

It’s important to note that temperature isn’t dependent on the number of molecules involved. A boiling cup of water has the same temperature as a boiling pot of water — both containers have water molecules with the same average kinetic energy, regardless of the quantity of matter involved.

Temperature scales

Credit: Flight Mechanic.

There are various scales used to describe temperature. In the United States, the most commonly used unit for temperature is Fahrenheit, while much of the rest of the world uses Celsius (or Centigrade). Physicists often prefer to measure temperature in Kelvin, which is also the standard international unit for temperature.

For the Kelvin scale, zero refers to the absolute minimum temperature that matter can have, whereas in the Celsius scale, zero degrees is the temperature at which water freezes at a pressure of one atmosphere (273.15 Kelvin). At 100 degrees Celsius, water begins to boil at a pressure of one atmosphere, offering a neat, linear and relatable scale for describing temperature.

A worthy mention goes to the Rankine scale, which is most often used in engineering. The degree size is the same as the Fahrenheit degree, but the zero of the scale is absolute zero. Often just R for “Rankines” rather than °R is used for expressing Rankine temperatures. The zero of the Rankine scale is -459.67°F (absolute zero) and the freezing point of water is 491.67R.

How temperature is measured

Because of our innate ability to sense how hot or cold things are, humans have had little use for precise measurements of temperature throughout history. However, there have always been mavericks bent on learning about things just for the sake of unraveling nature or getting a kick out of doing science.

Hero, a Greek philosopher and mathematician, is credited with the idea for the first thermometer, writing in the 1st century CE about the relationship between temperature and the expansion of air in his work Pneumatics.

The ancient text survived the degradation of the Roman Empire and the dark ages that followed, until it resurfaced during the Renaissance.

An assortment of Galileo thermometers of various sizes. The bigger the size, the more precise the instrument. Credit: Amazon.

It is believed that Hero’s work inspired Galileo Galilei to invent the first device that precisely measures temperature. The Galileo thermometer is composed of multiple glass spheres each filled with a colored liquid mixture that often contains alcohol but can even be simply water with food coloring added.

Each bubble has a metal tag attached to it that indicates temperature, which also serves as a calibrated counterweight that’s slightly different from the others. These floating balls sink or float inside the surrounding water sinking or climb up the water column slowly and gracefully. People still use them to this day, mostly for decorative purposes.

For more precise measurements, there’s the traditional mercury thermometer whose fluid expands at a known rate as it gets hotter and contracts as it gets cooler. It’s then just a matter of reading the measurement indicated by where the column of liquid ends on the scale.

Robert Fludd, an English physician, is credited with designing the first thermometer in 1638 that had a temperature scale built into the physical structure of the device. Daniel Fahrenheit designed the first mercury-based thermometer in 1714 that ultimately went on to become the gold standard of temperature measurement for centuries.

We’ve just had the warmest January ever recorded. Ever

We’re starting the year in force, according to data published Tuesday by Copernicus, the European Union’s climate change monitoring agency. January 2020, they explain, showed the highest average temperatures of any January on record.

Surface air temperature anomaly for January 2020 relative to the January average for the period 1981-2010.
Image credits Copernicus Climate Change Service / ECMWF.

“Last month the global temperature was warmer than any previous January in this data record, although almost on par with January 2016 (at 0.03°C warmer),” the agency said in a statement.

For Europe, it was about 0.2ºC warmer than the previous warmest January in 2007, and 3.1°C warmer than the average January in the period 1981-2010, the statement adds.

Large areas of north-eastern Europe recorded especially-high temperatures above the 1981-2010 January average, in some areas by more than 6°C. While the Carpathian Basin and several areas of southern Europe experienced temperatures “a little below normal” on average, mean temperatures in January were higher above the 1981-2010 average over most of Europe.

It has to be said by this point that 2019 put a wrap to the warmest decade on record to date; it was also the second-warmest year since recordkeeping began.

Copernicus used 2016 as a comparison because, until now, it held the unenviable title of ‘warmest year ever’. Still, average temperatures in 2016 were pushed up by a powerful El Niño — which 2019 didn’t have.

Not good news, everyone. Not good.

Body temperatures have dropped in the past century, and it’s probably because our lives are better

An intriguing study shows that body temperatures seem to be dropping by 0.03°C per decade — which over the last century, makes for quite a sizeable difference.

Human body temperature is not fixed. It fluctuates all the time, not only when you get feverish. It’s influenced by hormones, metabolism, and even your mood. Nevertheless, 37°C (98.6 F) was considered the average normal.

That is no longer the case.

“Our temperature’s not what people think it is,” said Julie Parsonnet, MD, professor of medicine and of health research and policy. “What everybody grew up learning, which is that our normal temperature is 98.6, is wrong.”

It’s not the first time this has been brought to light by researchers. A recent study carried out on 25,000 British participants found that the average temperature is 36.6°C (97.9 F). In a new study, Parsonnet and colleagues analyzed trends relating to body temperature, finding that the temperature has decreased slowly but steadily over the years.

They used data from three national US cohorts, summing up almost 200,000 people: the Union Army Veterans of the Civil War (1860–1940), the National Health and Nutrition Examination Survey I (1971–1975), and the Stanford Translational Research Integrated Database Environment (2007–2017). They found that even after adjusting for age, height, weight, and time of day, has decreased by about 0.03°C per decade.

Researchers also considered the possibility that measurements have simply gotten more accurate — as thermometry has improved massively since the 19th century. However, even within the same cohort (Union Army Veterans of the Civil War), the same trend was observed, which essentially rules out the possibility of measurement bias. Additionally, if this were the case, the change wouldn’t be linear and would have tapered out as accuracy reached a certain degree.

These trends have been suggested before, but this new model paints an intriguing picture. The temperature of men born in the 2000s is, on average, about 1.06 F (0.58 °C) lower than that of men born in the early 1800s. For women, the difference is only 0.58 F (0.58 °C)

Which begs the question, why is this happening?

Researchers aren’t entirely sure, but they have a few good ideas. Resting metabolic rate is the largest component of a typical modern human’s energy expenditure, typically comprising over 65% of daily energy expenditure for a sedentary individual. Much of this energy is converted into heat — this is what makes humans (and many other creatures) warm-blooded. If we’re observing less heat, this could be an indication that our metabolic rates have decreased, perhaps as we’ve become less and less physically active.

Comfortable lives in our warm houses may have a role to play. Homes in the 19th century had irregular heating and no cooling, whereas today, central heating has become commonplace in the developed world. A more constant environment removes a need to expend energy to maintain a constant body temperature, which could also help explain this effect.

However, the team thinks something else is likely at play: the reduction of inflammation. Economic development, along with improved standards of living and sanitation, decreased chronic infections, antibiotics, improved dental hygiene, along with a reduction of diseases such as tuberculosis, have all made us much healthier. This means that there’s less likely for our bodies to experience inflammation, which raises body temperature.

Whichever the case may be, this is a reminder that our bodies are slowly changing. The environment in which we are living is changing, our lifestyle is changing, and we are changing as a result.

“Physiologically, we’re just different from what we were in the past,” Parsonnet said. “The environment that we’re living in has changed, including the temperature in our homes, our contact with microorganisms and the food that we have access to. All these things mean that although we think of human beings as if we’re monomorphic and have been the same for all of human evolution, we’re not the same. We’re actually changing physiologically.”

The study “Decreasing human body temperature in the United States since the industrial revolution” has been published in eLife.

Australia records its hottest day ever — while burning from a thousand bushfires

This week, Australia has experienced its hottest day on record. Authorities expect the current heatwave to worsen, however, and further feed the bushfire season — which is already unprecedented as well.

With a nationwide average temperature of 40.9 degrees Celsius (105.6 degrees Fahrenheit), this Tuesday set a new record for the land down under. The previous record of 40.3 degrees Celsius was recorded in January 2013.

The heat is on

This year, Australia’s summer bushfire season has experienced a very early and intense start. Hundreds of fires have been roaring across the nation for months now, including a “mega-blaze” north of Sydney, the country’s largest city. Smoke from this blaze has led to increased levels of air pollution in Sydney, prompting authorities to declare the event a public health emergency.

All in all, over three million hectares (7.4 million acres) of land has been burned across Australia so far. Six people have lost their lives to the blaze, and about 700 homes have been destroyed.

Global warming is likely fanning the flames higher and earlier than usual. Australia has also experienced a prolonged drought, leaving a lot of dry plant matter in the bush, and leaving several towns out of water. The fires have sparked climate protests targeting the conservative government, which has resisted calls to address the root causes of global warming — in favor of the country’s lucrative coal export industry.

The heatwave started in the country’s western reaches, where firefighters were engaging thousands of bushfires earlier this week. It has since crept across central Australia and is spreading to the heavily populated eastern states. Weather forecasts for parts of New South Wales, of which Sydney is the capital estimate temperatures in the mid-40s Celsius (around 110 Fahrenheit) for the end of the week. On Saturday parts of Sydney are expected to reach over 46 degrees celsius (115 Fahrenheit).

Most bushfires so far have been recorded in Australia’s eastern states. Turbulent winds of up to 100 kilometres (60 miles) an hour are expected in the area later this week, which may further stoke the fires. Embers from the fires can travel up to 30 kilometers (around 18.5 miles) by strong winds, authorities explained, which further increases the risks during this time.

“Over the next few days we are going to see firefighters, the emergency services and all those communities close to fires […] challenged with a new threat,” New South Wales fire commissioner Shane Fitzsimmons said on Wednesday.

On Wednesday, police officers evacuated residents from dozens of homes in the Peregian area (northeastern Queensland) as out-of-control bushfires threatened the properties.

“Fire crews and waterbombing aircraft are working to contain the fire but firefighters may not be able to protect every property,” Queensland Fire and Emergency services said. “You should not expect a firefighter at your door. Queensland Police Service are door knocking in the area. Power, water, and mobile phone service may be lost.”

While Prime Minister Scott Morrison is on holiday at an undisclosed, overseas location, climate protesters plan to march in Sydney this week to demand change and highlight his absence as vast stretches of Australia burn. Recently, Mr. Morrison has acknowledged climate change as one of “many other factors” driving the bushfires.

New climate models show that global warming will be faster than expected

Things are about to get hotter than we expected.

Image via Pixabay.

New research suggests that the greenhouse gases we’re putting into the atmosphere by burning fossil fuels will heat the planet more quickly than we assumed. By 2100 mean temperatures could rise 6.5 to 7.0 degrees Celsius above pre-industrial levels if carbon emissions continue unabated, according to two separate models from leading research centers in France.

Tres hot

“With our two models, we see that the scenario known as SSP1 2.6 — which normally allows us to stay under 2°C — doesn’t quite get us [the intended results],” Olivier Boucher, head of the Institute Pierre Simon Laplace Climate Modelling Centre in Paris, told AFP.

The 6.5 to 7.0 degrees Celsius mark is two degrees higher than the equivalent scenario (SSP5) set out in the Intergovernmental Panel for Climate Change’s (IPCC) 2014 benchmark 5th Assessment Report. This difference in temperatures comes from refined predictions based on more complex and reliable climate scenarios, the team explains. They also suggest that the Paris Agreement goals of capping global warming at “well below” 2°C, and 1.5°C if possible, will be harder to reach, the scientists said.

It may not seem like a lot, but you have to keep in mind that the recent uptick in deadly heat waves, droughts, floods, and the intensity of tropical cyclones we’ve been seeing lately are happening with barely one degree Celsius of warming.

The two new models are part of a generation of around 30 new climate models collectively known as CMIP6; these will be used as a base for the IPCC’s next major report, scheduled for 2021. While they’re definitely not perfect, the models in CMIP6 are the best and most refined of their kind that we have. Their advantages include increased supercomputing power and sharper representations of weather systems, natural and man-made particles, and how clouds evolve in a warming world.

“We have better models now,” said Boucher. “They have better resolution, and they represent current climate trends more accurately.”

One of the core findings of these models is that increased CO2 levels in the atmosphere will warm Earth’s surface more easily than earlier calculations had suggested. The higher “equilibrium climate sensitivity” (or ECS) predicted by the models means that humanity’s carbon budget — how much we can emit before we see negative effects — is smaller than we previously assumed. Boiled down, a higher ECS means a greater likelihood of reaching higher levels of global warming, even with deeper emissions cuts.

Needless to say, this is bad news for global efforts to curb climate change.

The two French climate models, including one from France’s National Centre for Meteorological Research (CNRM), are to be unveiled at a press conference in Paris.

Researchers finally figure out the protein that senses cold temperatures

New research is homing in on the biochemical mechanisms that allow mammals to feel cold.

Image credits Antonio Jose Cespedes.

The study is the first to identify a protein that responds to extreme cold. The gene is evolutionarily conserved across species, including humans.


“Clearly, nerves in the skin can sense cold. But no one has been able to pinpoint exactly how they sense it,” said Shawn Xu, a faculty member at the University of Michigan Life Sciences Institute and senior author of the study. “Now, I think we have an answer.”

It’s vital for our bodies to be able to perceive temperature. When it gets too chilly outside, we need to feel that uncomfortable ‘cold‘ sensation so that we’ll seek shelter, warmth, and not die from exposure.

It falls to receptor proteins in the nerves of our skin to perceive this change and then relay the information to our brains. This mechanism holds true from humans down to very simple organisms, such as the millimeter-long worms that researchers study in Xu’s lab at the Life Sciences Institute: Caenorhabditis elegans.

We seek warmer environments when we’re cold, and Xu’s worms do the same thing: when they sense cold, they engage in avoidance behavior and move away, seeking warmth. However, unlike us, C. elegans have a simple and well-mapped genome, and a short lifespan, making them a valuable model system for studying sensory responses.

Previous efforts to find the receptor for cold have been unsuccessful because researchers were focusing on specific groups of genes that are related to sensation, which is a biased approach, Xu said. Instead, he and his team relied on the simplicity of C. elegans for an ‘unbiased approach’.

The team looked across thousands of random genetic variations to determine which affected the worms’ responses to cold. They report that worms engineered to lack the glutamate receptor gene glr-3 no longer responded when temperatures dipped below 18 degrees Celsius (64 F).

Glr-3 is responsible for making the eponymous GLR-3 receptor protein; without this protein, the worms lost sensitivity to cold temperatures, a strong indicator that it underpins the ability to sense cold.

The glr-3 gene is evolutionarily conserved across species including humans. The vertebrate versions of the gene can also function as a cold-sensing receptor, the team adds. The team determined this after adding the mammalian version of the gene to mutant worms lacking glr-3 (and were thus insensitive to cold), which made them feel cold temperatures once more.

The team also added the worm, zebrafish, mouse, and human versions of the genes to cold-insensitive mammalian cells, and all allowed the cells to sense to cold temperatures.

The mouse version of the gene, GluK2 has been documented to help transmit chemical signals within the brain. The authors further discovered that the gene is also active in a group of sensory neurons that detect environmental stimuli, such as temperature, through sensory endings in the mice’s skin. Reducing expression of GluK2 in these sensory neurons made the mice insensitive to cold, but not cool, temperatures — additional evidence that the GluK2 protein serves as a cold receptor in mammals.

“For all these years, attention has been focused on this gene’s function in the brain. Now, we’ve found that it has a role in the peripheral sensory system, as well,” Xu said. “It’s really exciting. This was one of the few remaining sensory receptors that had not yet been identified in nature.”

The paper “A Cold-Sensing Receptor Encoded by a Glutamate Receptor Gene” has been published in the journal Cell.

Extreme heat to become the new normal in the US

If there’s one clear sign of climate change, it’s extreme heat. And people all across the US know it as they have been facing it this summer with long heat waves. According to new research, this will likely be the new normal across the country.

A weather forecast in the US shows days with extreme heat. Credit: Flickr


Climate change will probably make extreme heat conditions and their health risks much more frequent in almost every part of the US, according to research published in the journal Environmental Research Communications.

“Our analysis shows a hotter future that’s hard to imagine today,” study co-author Kristina Dahl, a climate scientist at the Union of Concerned Scientists, said in a statement. “Nearly everywhere, people will experience more days of dangerous heat in the next few decades.”

By 2050, hundreds of US cities could see around 30 days each year with heat index temperatures above 100 degrees Fahrenheit (37.7 Celsius) if nothing is done to rein in global warming. The heat index is what the temperature feels like to the human body when relative humidity is combined with the air temperature — so it’s a measure of how temperature actually feels.

This is the first study to take the heat index — instead of just temperature — into account when determining the impacts of global warming. The number of days per year when the heat index exceeds 100 degrees will more than double nationally, according to the study.

“We have little to no experience with ‘off-the-charts’ heat in the U.S.,” said Erika Spanger-Siegfried, lead climate analyst at the Union of Concerned Scientists and report co-author. “These conditions occur at or above a heat index of 127 degrees. Exposure to conditions in that range makes it difficult for human bodies to cool themselves.”

The research suggests that there will be few areas of the country able to avoid these extreme heat events, except for some high-altitude mountainous regions. Currently, the only place that experiences these “off-the-charts” days is the Sonoran Desert on the border of southern California and Arizona.

The National Weather Service of the US typically issues a “heat advisory” when a maximum heat index is expected to hit at least 100°F for two or more days, and an “excessive heat warning” when it will hit at least 105°F for two or more days. These heat levels can lead to health risks such as dehydration and heatstroke.

The expected increase in heatwaves will require additional efforts to help people cope, especially those who aren’t used to it, the study concluded. This should be in line with a further reduction in global greenhouse emissions, now considered not sufficient to meet the 2ºC global warming limit established by the Paris Agreement.

Schematic of the working principle behind the temperature-sensitive polymeric gel microparticles. Credit: Nature.

Smart windows allow or block heat-generating wavelengths of light based on temperature

Schematic of the working principle behind the temperature-sensitive polymeric gel microparticles. Credit: Nature.

Schematic of the working principle behind the temperature-sensitive polymeric gel microparticles. Credit: Nature.

Researchers at MIT have devised polymer gels that are fitted inside double-pane windows, allowing or blocking near-infrared light from entering a building. The gel’s properties are regulated by temperature, so the whole process is automatic once a certain thermal threshold is breached. About half of all energy used by households in the United States is used for heating and cooling, so this kind of technology could have a tremendous impact on energy efficiency if adopted on a large scale.

When it gets too sunny outside, most of us use blinds and curtains to keep things inside a bit cooler. In order to remove the human factor (and make cooling a home or office more energy efficient), some engineers have devised electrochromic windows, which darken when a small electrical potential is applied. You’ll find such windows on a Boeing 787 Dreamliner, for instance. Typically, electrochromic windows require a human to activate a switch, although some applications allow the windows to darken automatically in response to temperature read by a third-party sensor.

The problem with electrochromic windows is that they are quite expensive, not very durable, and have inconsistent light-blocking properties. There are, however, windows whose light-penetrating properties are tuned directly by temperature. Previous attempts involve films of vanadium dioxide, a thermochromic compound with sunlight-modulating properties. Its main drawback is that it becomes activated at temperatures in excess of 90 °C, which makes it impractical for real-world use. And when they’re not activated, they only allow little light to come through, having a transmittance of around 50% (semi-opaque).

Researchers now report a novel thermochromic system that is a lot more reliable than previous demonstrations and might actually be practical for widespread use in homes and offices. The smart windows developed by the MIT researchers are based on polymeric gel particles (microgels) trapped between two glass panels. These gels have an extremely uniform density and a structure that forces the particle to swell in water in response to temperature. At 25 °C, the microgel particles have a diameter of 1.4 micrometers, scattering very little light and making the window highly transparent. Above 32 °C, the microgels collapse and expel water, scattering light in the infrared red range (the kind we perceive as heat).

In experiments, the researchers showed that their system achieved an infrared transmittance of 81.6% in the inactivated transparent state, but only 6% when activated. As a result, the temperature inside a test chamber fitted with microgel-based smart windows had a significantly lower temperature compared to a chamber fitted with standard double-pane windows. The smart windows had no noticeable loss in performance after switching between states more than 1,000 times. They’re also not affected by freezing. Finally, the microgels and window assembly are not prohibitively expensive, making the technology promising for real-world applications.

The major drawback is that once activated, the gels make the window relatively opaque because they also scatter ultraviolet and visible frequencies in the spectrum of light. Another drawback is that in the evening, because it’s cool outside, the windows remain fully transparent, reducing privacy. The whole idea is to stop using curtains, so as they stand today, these sort of smart windows may not be practical in all situations.

The system was described in the journal Joule.

This April was Earth’s 400th consecutive warmer-than-average month

Temp departure baseline.

Image credits: NOAA.

According to the last monthly climate report published by the National Oceanic and Atmospheric Administration (NOAA), the Earth has had about 33 years of above-average temperatures. The last colder-than-average month (across land and ocean surfaces) was recorded in December 1984, during US President Ronald Reagan’s second term.

The document also notes that April 2018 was the third-hottest April NOAA ever recorded since it started gathering climate data in 1880. Nice of the top ten warmest Aprils on record have now occurred since 2005, it adds. The root cause is, unequivocally, human activity.

“It’s mainly due to anthropogenic (human-caused) warming,” NOAA climatologist Ahira Sanchez told CNN. “Climate change is real, and we will continue to see global temperatures increase in the future.”

We’ve made real effort to decouple from the use of fossil fuels and reduce emissions in the last few years. However, little headway has been made so far. Developed countries are seeing significant push-back at multiple levels of society: government lobby in favor of oil, gas, and coal; faulty, pro-fossil scientific papers; a gross manipulation and politicization of the issue in the eyes of the public.

Developing nations are also arguing for their right to increase emissions, as they want to mirror richer countries and rapidly expand their economies, technological base, and population through the use of fossil fuels.

To see how the climate is faring, the team used 20th-century average measurements as a benchmark value. This allowed them to set a standard to compare today’s conditions against. At the same time, it allowed them to account for natural climate variability. The results show that every month in the last few decades showed higher than average temperatures “by whatever metric,” according to NOAA climate scientist Deke Arndt.

Climate anomalies.

Annotated map of the world showing notable climate events that occurred during April 2018. Image credits NOAA / NCEI.

“We live in and share a world that is unequivocally, appreciably and consequentially warmer than just a few decades ago, and our world continues to warm,” Arndt adds. “Speeding by a ‘400’ sign only underscores that, but it does not prove anything new.”

The gross of the overall emissions comes from developed countries — that’s how they became developed in the first place, by burning fossil fuels. Still, presently, the bulk of emissions come from developing nations, NOAA notes. In other words, we can’t pin the blame on them.

The rise in temperatures isn’t uniform, NOAA’s report adds. Europe seems to have borne the brunt of the extra heat, with the last month being the warmest April ever recorded on the continent. Heat waves also hit Australia, which saw the second-warmest month ever recorded in the land down under. Asia also saw episodes of extreme heat. The document cites the example of the town of Nawabshah in southern Pakistan, where thermometers hit an incredible 122.4 degrees Fahrenheit (roughly 50.5 Celsius) on April 30th. On the flipside, North America had its 15th coldest April, tied with 1918. Yet despite America’s unusually cold winter, globally, temperatures were still abnormally high.

All in all, these extreme temperatures have raised the global average temperature this April by 1.49 degrees Fahrenheit above the 20th-century average — topped only by 2016 and 2017, which were 1.94 degrees Fahrenheit and 1.60 degrees Fahrenheit above average, respectively. NASA backs up these conclusions.

Two other agencies, the Japan Meteorological Agency (JMA) and the Copernicus Climate Change Service — operated by the European Centre for Medium-range Weather Forecasts — also calculated that April 2018 was the third-warmest on record.

The document also reported that carbon dioxide levels in the atmosphere passed the 410 ppt mark — the highest levels since the Pliocene. The data is further supported by readings from the Scripps Institute of Oceanography, which we’ve previously reported on here.



The number of ocean heatwaves has risen more than 50% since 1925, threatening to collapse marine ecosystems

Ocean-dwellers have to brave through heat waves too — according to a new study, much more often than we’d believed. The incidence of such events increased by 54% from 1925 to 2016, and their frequency has risen by nearly 35% over the same period, the paper reports.


Image via Pixabay.

As the Earth heats up, mean ocean temperatures have also been steadily rising. This latter change makes it easier for extreme marine heating events — similar to heat-waves, but involving bodies of how water instead of air — to occur. Compared to air, however, water can absorb far more heat and is better at retaining it, making marine heatwaves long-lived periods of extreme temperatures.

One example of such an event took place in the Pacific in 2015: water temperatures surged by as much as 10 degrees Fahrenheit (5.55 Celsius) above average in an area stretching from Alaska to Mexico. It might not sound like much of a difference, but for marine life, it was almost unbearable. Animals from a number of sea-dwelling species, including sea lions and birds, died to the heat. There were also nearly 50 reported cases of whale deaths that are believed to be linked to the heatwave.

Boil, broil, heat, and toil

Heat waves tend to be one of the most deadly weather phenomena on dry land. One such event claimed the lives of about 70,000 Europeans in 2003, most of those deaths occurring in only two months, July and August (when the predominant rise in temperatures was recorded).

Although marine heat waves are far less studied or understood, we still do know that they are just as devastating as their land counterparts (which are set to become worse, both in Europe and the USA). Waves of extreme heat, among other things, bear the lion’s share of responsibility for coral bleaching events. For example, such events repeatedly battered Australia’s Great Barrier Reef until 2016, when one heat wave pushed the ecosystem past its limit, killing off nearly 70% of corals in a 430-mile area of (what we considered to be a) pristine reef. In essence, it was the final blow to an ecosystem already shaking after prolonged exposure to abnormally high temperatures.

To get a better understanding of such events, the team pooled together data on sea surface temperatures stretching back to over a century ago. Despite the wealth of recordings they had at their disposal, the team noted that the ‘best data’ (as in, the most reliable and comprehensive) comes after 1982, specifically satellite-recorded data collected by National Oceanic and Atmospheric Administration (NOAA) over the course of over 30 years.

The team suggests that climate-change-induced rises in global temperatures, which drove an increase in average ocean temperatures, is behind this increase in marine heatwaves. Having warmer oceans simply makes it easier for temperatures to fall to extremes and make such events possible, they note.

We’re causing it

Marine heatwave days chart.

Globally averaged time series of total marine heatwave (MHW) days from 1982 to 2016 (NOAA dataset).
Image credits E. Oliver et al., 2018, N.Comm.

The most reliable and accurate part of the dataset (1982-2016) falls a bit on the short side, and so it can’t be used to draw an unassailable link between the two. In other words, while the findings point to anthropic climate change as the main driving force behind the increase in marine heat wave, they can’t specifically rule our natural temperature swings right now.

However, the team notes that the increase in average ocean temperatures is inarguably linked to human activity. The man-made greenhouse effects increase the overall quantity of incoming solar radiation that remains trapped, and roughly 95% of that radiation is absorbed by the oceans.

In light of how things are going right now, this means that ocean temperatures will almost certainly continue to rise this century. Though there is a global push to mitigate the release of greenhouse gases into the atmosphere, we’re still releasing a lot. The ones already floating around will also take time to break down, so it will take time for our efforts to yield results. Lastly, there’s the problem of willingness: the US, the second-largest single emitter of greenhouse gasses, and the largest per capita emitter don’t seem interested in playing ball in this regard — if anything, the current administration seems determined to undermine as many climate regulations as it can.

Still, the team is confident that a global, concerted effort to limit powerful greenhouse gas emissions would help limit the severity of ocean temperature increase.

Future extreme warming events in the oceans will be especially likely to occur during longer-term (i.e. measured in years or more) warming trends, the team notes. These include El Niño events in the Pacific Ocean and the Pacific Decadal Oscillation, which can warm vast regions of the Pacific Ocean for decades. The main concern is that — piled over the growing pollution, overfishing, and acidification issues — marine heat waves might push tip the ocean’s ecosystem beyond their tipping point.

The paper “Longer and more frequent marine heatwaves over the past century” has been published in the journal Nature Communications.

July 2090 high emissions.

Chilling maps show just how scorching 2090’s US will be, thanks to climate change

In an effort to show the actual effects climate change will have on each of our lives in the future, the National Oceanic and Atmospheric Administration (NOAA) put together some chilling maps showing a scorching future.

Melting ice cream.

“Melting Ice Cream Truck” by Glue Society.
Image via thisiscolossal.

Climate change is going to cause a whole lot of changes to the world as we know it. Sea level rise, species extinction, and food and water uncertainty for many. While we’re aware of these future threats, the problem is that we’re just not very good, from a psychological point of view, at dealing with future problems that require collective action.  It doesn’t feel like it matters to us directly, it doesn’t feel like we can do anything about it, so we don’t really care. Our brains sport more of a cross-that-bridge-when-we-get-there type of wiring.

That, in the context of climate change, is a really bad strategy. It takes time for this damage to build, but it takes just as long for us to work on preventing it — and much longer to fix it after the deed is done.

Would you like some ice with that?

NOAA, however, knows what’s up. NOAA is also sneaky and knows what everybody hates: scorching summer temperatures. So, to help us better understand what path we’re walking down, they’ve compiled some maps to show just how hot things are going to get by the end of the century. For example, here’s what mean July temperatures looked like in the US in 2010 — and how they will look in 2090.

Scorching, right? Well, don’t take out the ice-cubes just yet because this is one of the better-case scenarios — one where we pursue and achieve fairly ambitious reductions in greenhouse gas emissions and reforestation. Yep, fairly ambitious greenhouse gas reduction and reforestation. With the new, 2.0, ‘clean’ coal administration currently ruling the US, neither of those targets seem very likely, do they?

NOAA agrees; that’s why they’ve also made predictions for a business-as-usual scenario, in which we keep polluting as we do now, and make no policy changes in regards to the environment. If we go down that road, July 2090 looks like a time where no amount of ice cream will cut it:

July 2090 high emissions.



For those of you with an unnatural fear of metrics, deep red (the thing covering most of the US in the picture) corresponds to average daily highs of 100°F (37.8°C). Daily. For a month at least, year after year, after year. I don’t know about you guys, but when I see the thermometer hitting 30°C I know it’s going to be a bad day. At 35°C, I can’t function any longer. I just fill my bathtub with cold water and camp in it.

I’m not so special in that regard; people and high temperatures don’t seem to mix that well. Currently, some 658 people die from extreme heat in the US every year, mostly in states such as Arizona or Texas. That number is bound to skyrocket as these states themselves, along with the rest of the US, start getting hotter.

Winters will also warm up. Even under a best-case-scenario, average highs during winter months will look something like this (the video starts with current mean temperatures).

I like what NOAA did with these maps because I feel it helps put that infamous 2°C Paris goal into context. It’s often used as a reference point in many discussions around climate change, and a benchmark that many official bodies, scientists, and publications use — but it doesn’t convey much to the average Joe.

Knowing that global temperatures will increase by 2°C doesn’t sound like much, and there’s probably a lot of ‘globe’ around so that doesn’t tell me much about what I’m going to have to face. Even worse, that figure is the mean annual temperature — putting one more layer of abstraction between it and what effects I’ll feel.

Hopefully, NOAA’s work will help us better understand what’s waiting for us down the road. They note that most people in the US will have to contend with scorching heat as soon as 2050 — and such conditions will take their toll on the economy and our quality of life (high temperatures, among other things, make it harder for us to sleep).

Our lawmakers do have the power to change where we’re heading. Quite possibly, most of them don’t particularly care — but they do care about votes. Call them up, ask them why they want you to suffer through 100°F during lunch. Then ask why you should vote for them.

Scientists find link between obesity and body temperature

Scientists have found a potential connection between your ability to maintain your body’s temperature and obesity. But don’t go blaming obesity for those extra pounds just yet.

Screenshot of a video recording of IR thermography of a WT (left) and a TRPM8-deficient mouse (KO, right). Note the difference in the tails of the two mice. Image credits: Reimúndez et al., JNeurosci (2018).

As humans are warm-blooded animals, our bodies work vigorously, day and night, to keep our body temperature constant — and food plays an important role in that process. We don’t often think about it this way, but food is essentially fuel for our body. However, food does much more than just provide us with the energy to operate through the day.

A normal body temperature is around 37 degrees Celsius (99 Fahrenheit), though it may vary somewhat from person to person. Eating tends to lead to a slight increase in body temperature as your metabolic rate increases to allow the digestion of food. Depending on what and how much you eat, your body temperature may increase by as much as 1.1 degrees Celsius (2 Fahrenheit), as the chemical reactions associated with digestion kick in.

Rosa Señarís and colleagues from the University of Santiago de Compostela and the Institute of Neuroscience/University Miguel Hernandez of Alicante (Spain), analyzed a different connection between temperature and food intake. They studied a group of lab mice, disabling their a receptor called TRPM8, also known as the cold and menthol receptor 1 (CMR1). They found that in a mildly cold environment, mice lacking the cold-sensing TRPM8 consumed more food during the day, when mice are usually asleep. This change took place from a young age, and led to obesity and high blood sugar in adulthood. Researchers believe this may have been caused by reduced fat utilization.

This isn’t the first time something like this has been reported. In 2011, a team writing in The American Journal of Clinical Nutrition found that a “lower core body temperature set point has been suggested to be a factor that could potentially predispose humans to develop obesity.” In a 2015 study, researchers found that a “biological inability to create sufficient core body heat could be linked to the obesity epidemic,” concluding that a diurnal thermogenic handicap can play a crucial role in favoring weight gain in obese subjects. Both studies called for more research on the matter, but there seems to be growing evidence for this obesity-temperature connection.

The article ‘Deletion of the cold thermoreceptor TRPM8 increases heat loss and food intake leading to reduced body temperature and obesity in mice’ has been published in JNeurosci. DOI: https://doi.org/10.1523/JNEUROSCI.3002-17.2018

Heat and light.

External temperature also influences our circadian rhythms, study reports

It’s not only light that tells our biological clocks it’s time for bed — temperature plays a role, too.

Heat and light.

Image credits Leonardine36 / Pixabay.

Researchers from the University of Michigan report that even mild changes in ambient temperature can influence sleep-wake cycles. The neurons that regulate the body’s circadian clock use thermoreceptors to keep tabs on temperatures outside the body, and use the readings to determine when it’s time for a nap.

The findings help flesh out our understanding of how the mammalian brain regulates wake-sleep cycles; previously, only the influence of light on the circadian rhythm was known.

Chill down, nap on

“Decades of work from recent Nobel Prize winners and many other labs have have actually worked out the details of how light is able to adjust the clock, but the details of how temperature was able to adjust the circadian clock were not well understood,” said Swathi Yadlapalli, first author of the study.

“Going forward, we can ask questions of how these two stimuli are processed and integrated into the clock system, and how this has effects on our sleep behavior and other physiological processes.”

The circadian rhythm, also sometimes referred to as the circadian clock, is a biochemical mechanism that allows living organisms to sync their sleep-wake cycle to the 24-hour cycle of a day. Essentially, it’s our daily rhythm. One of the key factors influencing the workings of this rhythm, perhaps unsurprisingly, are levels of ambient light.

However, temperature also seems to play a big part. Together with Chang Jiang, a postdoctoral researcher at the U-M Department of Mechanical Engineering, Yadlapalli developed an optical imaging and temperature control system. Using it, the duo looked into the neural activity in the circadian clock of fruit flies (Drosophila melanogaster) while they were exposed to heat and cold. Fruit flies were used for the study because the neurons that govern their circadian clocks are strikingly similar to those in humans.

The team reports that colder temperatures excite sleep-promoting neurons, a process which ties external temperature to sleep cycles. Finding such a process in fruit flies suggests these neurons could have similar functionality in humans.

“It looks like clock neurons are able to get the temperature information from external thermoreceptors, and that information is being used to time sleep in the fly in a way that’s fundamentally the same as it is in humans,” Shafer said.

“It’s precisely what happens to sleep in mammals when internal temperature drops.”

Shafer adds that the circadian system creates a daily rhythm in temperature which is an important cue for when nap time comes around. So, while you may think our bodies run at a steady 37°C (98.6°F), “in fact, it’s fluctuating.” As the clock ticks nearer to wakefulness, our circadian system warms the body up. When it’s close to bedtime, it lowers our internal temperature. This effect is independent of the temperature of the room you’re sleeping in.

The paper “Circadian clock neurons constantly monitor environmental temperature to set sleep timing” has been published in the journal Nature.