Tag Archives: water vapor

lightning

Twice as many lightnings expected by 2100 as a result of global warming

Researchers from the  Lawrence Berkeley National Laboratory and the University of California, Berkeley, have devised a model that projects how climate change affects atmospheric lightning discharges. According to their findings, global warming – particularly through more water vapor gathering in the upper atmosphere – will cause lightning strikes to increase in frequency by 50% during this century.

More warming and lightning

lightning

Photo: Chris Kotsiopoulos / National

Lightning is one of the most powerful forces found in nature (if one single lightning strike was harnessed, the energy would power an entire home for a whole week), but at its core we can say that lightning is nothing but a discharge of static electricity. What we know from static electricity is that these discharges are caused by separation of charges into positive and negative ions.  Over time more of one charge builds until its natural attraction to the opposite charge causes it to migrate in an electrical discharge. In the case of lightning, the charge is built up in water. Clouds are made up of condensed water vapor, and one of water’s fantastic molecular properties is its ability to polarize charges.

Because one of the effects of global warming is an increase of water vapor in the atmosphere, it’s expected that thunders storms will intensify and become more frequent in the coming years. So far, we’ve yet to see a reliable model, but the latest predictions reported by US scientists seem to be getting there.

“With warming, thunderstorms become more explosive,” said David Romps, an assistant professor of earth and planetary science, in a statement. “This has to do with water vapor, which is the fuel for explosive deep convection in the atmosphere. Warming causes there to be more water vapor in the atmosphere, and if you have more fuel lying around, when you get ignition, it can go big time.”

The team looked at key atmospheric parameters and correlated these with lightning rates. Namely, they combined precipitation rates (total amount of water hitting the ground from rain, snow, hail or other forms ) and “convective available potential energy” (CAPE) into their model to retrieve a value for mass and energy flow through the ascending air—energy per kilogram per square meter per second.

“CAPE is a measure of how potentially explosive the atmosphere is, that is, how buoyant a parcel of air would be if you got it convecting, if you got it to punch through overlying air into the free troposphere,” Romps said. “We hypothesized that the product of precipitation and CAPE would predict lightning.”

Using actual data from 2011 gathered by weather satellites and radiosondes – ballon-borne instruments that measure CAPE –  calculated CAPE-times-precipitation for multiple locations in the continental United States. The product was then plotted against lightning rates for the same area. Results show that  CAPE-times-precipitation accounts for 77 percent of the observed variation in the tempo of cloud-to-ground lightning. Precipitation alone only accounts for 29 percent, which explains why other models that relied solely on precipitation as the feed-in parameter failed miserably at predicting lightning rates.

[AMAZING] Lightning in slow-mo – VIDEO in 7,207 frames per second

The team then used their model with data from 11 different climate model that predict precipitation and CAPE throughout the century. On average, the models predicted an 11 percent increase in CAPE in the U.S. per degree Celsius rise in global average temperature by the end of the 21st century. If atmospheric temperature is to rise by four degrees Celsius by 2100, as many models predict it to happen, then  a roughly 50 percent increase (+/- 25%) in lightning rate is expected.

Though not that many people die from lightning strikes on a yearly basis, the damage produced by wild fires induced by lightning is considerable. Lightning ignites about 10,000 wild fires each year in the US alone or 4.1 million acres.

Findings appeared in the journal Science.

 

global_warming

Study confirms global warming is moistening the atmosphere

Climate models have invariably predicted that the upper atmosphere would become moister as a result of global warming, the question remained whether these disturbances are natural or anthropogenic.  A new research that used satellite readings found that indeed rising vapor content in the upper troposphere comes as a result of man-made global warming. The findings further strengthen climate models and add to a body of evidence that supports anthropogenic climate change.

A wetter atmosphere

 

The authors write in the paper abstract, published in PNAS :

“Our analysis demonstrates that the upper-tropospheric moistening observed over the period 1979–2005 cannot be explained by natural causes and results principally from an anthropogenic warming of the climate. By attributing the observed increase directly to human activities, this study verifies the presence of the largest known feedback mechanism for amplifying anthropogenic climate change.”

The amount of water vapor in the atmosphere exists in direct relation to the temperature. If you increase the temperature, more water evaporates and becomes vapor, and vice versa. So when something else causes a temperature increase (such as extra CO2 from fossil fuels), more water evaporates. Then, since water vapor is a greenhouse gas, this additional water vapor causes the temperature to go up even further. Effectively, water vapor causes a positive feedback loop and it can get quite dangerous. According to skepticalscience.com, for every 1°C change caused by CO2, the water vapor will cause the temperature to go up another 1°C.

Climate change models predict a moistening of the atmosphere. Researchers at the University of Miami sought to make the first measurements and thus verify whether or not the model projections of anthropogenic climate change are genuine. Radiant heat was measured using satellite imaging and they found that it has changed over the past 30 years. This change could be attributed to increased temperature or water vapor, so to separate potential effects the researchers complemented their initial readings with others made at different wavelengths.

They then tested their findings using the best and most accurate to date climate models to see if the observed changes in moisture were due to natural changes in the Earth’s climate or man-made activity. Only human-emitted greenhouse gases matched the observations, causing the team to conclude:

“Concerning the satellite-derived moistening trend in recent decades, the relations of trend and associated range among three experiments lead to the conclusion that an increase in anthropogenic greenhouse gases is the main cause of increased moistening in the upper troposphere”

The findings are of great importance since it yet again proves that climate change models are accurate and adds to a pilling body of evidence supporting the man-made climate change.