Wednesday, February 14, 2007

Soils and its role in a changing climate

Roger Pielke Sr., over at his research group's climate science blog, has been holding forth on land use change and its impacts on long-term near surface temperature. His position is that the role of land use must be further emphasized within the climate change framework. Search for "soil" and "land" for a long list of supporting posts.

This goes beyond deforestation and urban heat islands. Dust and alterations in atmospheric water content play unknown roles and interact with albedo in sometimes counterintuitive ways. For example, irrigation warms rather than cools the land. Evaporative cooling is insufficient to drive net cooling of irrigated regions. Soils darkened by moisture absorb more heat than dry soils and re-radiate more heat during the night. This results in warmer nights and warmer average temperatures.

Current climate models are not sensitive to changes in land use. Neither are they sensitive to the soil's role in affecting atmospheric carbon levels.

Soil organic matter, at roughly 1500 GtC, is the single largest compartment of carbon in the active biogeochemical cycle. At 60 GtC annual flux (in either direction), it is 10 times larger than the 5.5 GtC flux due to burning fossil fuel. Yet soil is the component of the carbon cycle that we know the least about.

Most soil scientists agree with the unvalidated concept that soil carbon levels will likely decline in step with temperature increases. Higher biological activity will result in more decomposition of organic matter. One certainly sees a similar relationship between soil carbon and temperature when comparing the effect of elevation, aspect and latitude. That we have yet to validate it is telling.
Current climate models mostly ignore the specific role that soil microbes play in the release of carbon dioxide into the atmosphere. The information they do include is often based on assumptions that have never been tested in the field, and may be wrong or overly simplistic.
Our climate models are telling us we need to become far more efficient and more conservative in managing our planet's carbon, soil-wise and fuel-wise. But our scientific understanding will never be adequate for crafting our full response to climate change.
The fact is that our climate is infinitely complex. The models climatologists use to predict the future are incredibly sophisticated, yet blunt instruments. Scientists can never account for all the variables involved - indeed, no one has successfully come up with a mathematical equation to describe the formation of a single cloud. And scientists are often woefully out of their depth in the real world. History is littered with lives and regimes that were wrecked when science was allowed to drive policy with no thought to humanity. Tearing down the global carbon-based economy to - in theory - replace it at a later date with unproven and undeveloped technologies would be a similar folly. It is only by tempering science with economics and the market, which is the most efficient arbiter of humanity's wants and needs, that smart climate policy can be made.
Science and the market are partners of longstanding. Economic necessity, as the mother of invention, has been driving the advance of science for as long as science has been an identifiable pursuit.

Distorted Vision
Originally uploaded by uaezlulu.

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