The Hot Zone

What a degree means

Posted by Alison Hawkes on July 23, 2010
Category : The man made climate

Climate change scenarios are usually summed up in terms of expected change by a certain year. Like sea levels will rise by x amount by 2020 and y amount by 2050. Or by parts per million of CO2 in the atmosphere.

But because no one really knows what kind of carbon dioxide increases we’re facing (that having to do with the CO2 cutting regimen we choose), the whole forecasting effort becomes very ambiguous. That’s led some to throw their hands up on achieving greenhouse gas reductions in favor of adaptation planning.

A new report issued by the U.S. National Research Council takes a different approach. It orients climate change scenarios to degree increase in temperature to show what each degree gets you in impact.

“An important reason for using warming as a reference is that scientific research suggests that many key impacts can be quantified for given temperature increases,” the report states.

It’s a very nuts and bolts approach, allowing for people to see clearly the consequences of each degree of warming and determine what is the acceptable level of risk. For members of Congress debating a climate change bill, the report provides a handy reference point for making decisions that will impact the Earth for centuries or longer.

Image from NASA.

Let’s look at food production. Depending on the species and other factors like rainfall, many crops respond well to a 1-2 degree C temperature increase. Anything higher and things start to look dicey.

Asian rice fairs comparatively well, but U.S. and African maize, Indians wheat, and U.S. soybean crops show a sharp drop-off in yield. U.S. maize will see a stunning 11 percent drop in yield per degree C  of warming. That doesn’t sound good. Not only does that feed Americans, but about 40 percent is currently exported to fill bellies in the rest of the world.

Climate change will increase world hunger.

One  degree C warming also increases wildfires in the western U.S. by 200-400 percent, depending on location and available fuel. It was also reduce rainfall in the American Southwest, Mediterranean, and southern Africa by 5 -10 percent.

Wildfire in Santa Clarita, California in October 2007.

Under a 2 degree C temperature increase, the southwest and central part of the U.S. would see three times the number of high heat days, exceeding 38 degree C or 100 degree F. You get the picture.

Climate change skeptics often minimize the impact of a couple degrees increase. Who doesn’t like warmer weather? But put in concrete terms, we may one day miss the comfort of a cold winter day by the fire. Or in California, a bleak, foggy day spent in a cafe.

-Alison Hawkes

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