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What are the global consequences of all the fires burning in the Northern Hemisphere (i.e. Western U.S., Russia etc.) Would there be any connection with the amount of rain for the season, since water vapor must have something to condense on. THANK YOU
Question Date: 2002-09-10
Answer 1:

That's a great question. I love fire questions.

Some climate effects might be increased temperature. One reason is that evapotranspiration will be a lot lower. This big word means the water that is pulled out of the soil by plants evaporating off of leaves. It takes a lot of energy to turn liquid water into a gas (water has a high "specific heat"). This energy comes from heat. It's the same principle that makes you cool by sweat evaporation. Evapotranspiration can have an important influence on temperature. How else would tree removal increase temperature? I'll give you a hint about one way: what color will the burned material be, and how does this relate to heat? There's at least one other way that you're very aware of, but might have to think about. Wind may increase with fewer things to block it, and erosion may be a problem. On a larger scale, fires add CO2 to the atmosphere. They also remove plants that remove CO2 from the atmosphere during photosynthesis. Increased CO2 can contribute to a global increase in temperature.

There's a whole lot of information about that on the Internet, just don't confuse it with the "ozone hole." Fires aren't all bad though. What are the benefits of forest and grass fires? Thanks for asking.

Answer 2:

Good question, and not an easy one to answer. As I'm sure you know, the main effect of fires on the climate system is the release of dust particles and aerosols into the atmosphere. (The release of carbon dioxide and other greenhouse gases is also significant but has a less severe immediate effect.) As a rule of thumb, aerosols tend to cool the climate system, because they scatter some fraction of incoming sunlight back out to space. For example, large volcanic eruptions such as Mt. Pinatubo in 1991 (1992?)result in reduced temperatures for the next 1-2 years, until the aerosols act as nucleation points for water vapor and are rained out of the atmosphere.

But this is only a rough rule and in general the aggregate effect of aerosols on the climate system are not well known. In fact, aerosols and aerosol-cloud feedbacks are probably the major sources of uncertainty in our modelling of the present and future climate system. For more information about the effects of aerosols on future climate predictions, see the Intergovernmental Panel on Climate Change's.

Sorry to not be able to give a more definitive answer but this is a real scientific frontier right now and a lot of organizations are spending a lot of money studying this issue.



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