Marc Morano has alerted us to an interesting contradiction with respect to how landscape affects the climate system which he headlines “Subject: Which is it? Trees Cool Or Heat the Planet? Studies Give Contradictory Results “.
His comment is illustrated by the two studies:
1. Northern Forests May Increase Temperatures by 10 Degrees by 2100, New Study Says; Deforestation Could Cool the Planet [April 9 2007]
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“Forests on certain parts of the planet may actually warm the Earth, according to researchers from the Lawrence Livermore National Laboratory in a study released today.
According to the study, forests in mid- to high-latitude locations — such as boreal forests of Canada, Scandinavia and Siberia — may actually create a net warming. The study concludes that by the year 2100, these mid- and high- latitude forests may make some places up to 10 degrees Fahrenheit warmer than would have occurred if the forests did
not exist.
The research, led by Lawrence Livermore National Laboratory atmospheric scientist Govindasamy Bala, appears in the April 9-13 online edition of the Proceedings of the National Academy of Sciences.”
2. Chemical released by trees can help cool planet, scientists find : Scientists discover cloud-thickening chemicals in trees that could offer a new weapon in the fight against global warming [October 31 2008]
The text in this article states
“Trees could be more important to the Earth’s climate than previously thought, according to a new study that reveals forests help to block out the sun.
Scientists in the UK and Germany have discovered that trees release a chemical that thickens clouds above them, which reflects more sunlight and so cools the Earth. The research suggests that chopping down forests could accelerate global warming more than was thought, and that protecting existing trees could be one of the best ways to tackle the problem.
Dominick Spracklen, of the Institute for Climate and Atmospheric Science at Leeds University, said: ‘We think this could have quite a significant effect. You can think of forests as climate air conditioners.’
The scientists looked at chemicals called terpenes that are released from boreal forests across northern regions such as Canada, Scandinavia and Russia. The chemicals give pine forests their distinctive smell, but their function has puzzled experts for years. Some believe the trees release them to communicate, while others say they could offer protection from air pollution.
The team found the terpenes react in the air to form tiny particles called aerosols. The particles help turn water vapour in the atmosphere into clouds.
Spracklen said the team’s computer models showed that the pine particles doubled the thickness of clouds some 1,000m above the forests, and would reflect an extra 5% sunlight back into space.
He said: ‘It might not sound a lot, but that is quite a strong cooling effect. The climate is such a finely balanced system that we think this effect is large enough to reduce temperatures over quite large areas. It gives us another reason to preserve forests.’
The research, which will be published in a special edition of the Royal Society journal Philosophical Transactions A, is the first to quantify the cooling effect of the released chemicals. The scientists say the findings “must be included in climate models in order to make realistic predictions”.
What these two studies actually tell us is that
Humans can alter the Earth’s climate system in very signficant ways by changing the landscape. This important scientific conclusion has been essentially ignored in the IPCC and CCSP assessments.
An overview of this issue was reported on, for example, in
Pielke Sr., R.A., 2005: Land use and climate change. Science, 310, 1625-1626.