Friday, 16 July 2010
National Academy Of Sciences On What's To Come

New National Academy of Sciences report: Emissions cuts needed soon to stem global warming

July 16, 2010 by Ken Ward Jr.

A major new report out this morning from the National Academy of Sciences has some important findings for West Virginia leaders – such as Sen. Jay Rockefeller — who aren’t in any hurry to put a limit on greenhouse gas emissions.

The headline on the academy’s National Research Council news release sums it up well: “Near-term emissions choices could lock in climate changes for centuries to millennia.” According to the release:

Choices made now about carbon dioxide emissions reductions will affect climate change impacts experienced not just over the next few decades but also in coming centuries and millennia, says a new report from the National Research Council. Because CO2 in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe.

Here’s an example:

Currently the concentration of CO2 in the atmosphere is about 390 parts per million volume (ppmv), the highest level in at least 800,000 years. Depending on emissions rates, that level could double or nearly triple by the end of the century, greatly amplifying future human impacts on climate, the report says.

Because the amount of human-caused CO2 emissions already far exceeds the amount that can be removed through natural carbon “sinks” such as oceans, keeping emissions rates the same will not stabilize the concentration of CO2 in the atmosphere. Even if emissions held steady, the CO2 concentration in the atmosphere would increase, much like the water level in a bathtub when water is coming in faster than it is draining. Emissions reductions larger than about 80 percent, relative to whatever peak global emissions rate may be reached, would be required to approximately stabilize carbon dioxide concentrations for a century or so at any chosen target level.

Further, stabilizing atmospheric concentrations does not mean that temperatures will stabilize immediately. Warming that occurs in response to a given increase in the CO2 concentration is only about half the total warming that will ultimately occur. For example, if the CO2 concentration stabilizes at 550 ppmv, the Earth would warm about 1.6 C on the way to that level; but even after the CO2 level stabilizes, the warming would continue to grow in the following decades and centuries, reaching a best-estimate global “equilibrium” warming of about 3 C (5.4 F). Waiting to observe impacts before choosing a stabilization target would therefore imply a lock-in to about twice as much eventual crop loss, rainfall changes, and other impacts that increase with warming.

The report’s executive summary is here, and the entire report is available here.

Posted on 07/16/2010 2:30 PM by Hugh Fitzgerald
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