Significant Warming Unavoidable, Study Says

“We can no longer avoid significant warming during this century,” Warren Washington, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, said in a news release Tuesday announcing a new analysis of future climate scenarios churned out by supercomputers.

Left unchecked, global greenhouse gases are on track to reach concentrations of 750 parts per million in the atmosphere by 2100. This would push sea levels up 8.7 inches from thermal expansion; melt nearly all the Arctic sea ice; raise global temperature at least 4 degrees Fahrenheit; and cause dramatic shifts in rainfall patterns around the world, according to the analysis.

The good news is if nations cut greenhouse gases by 70 percent this century “we could stabilize the threat of climate change and avoid catastrophe,” Washington said. Sea levels, not counting melting ice sheets and glaciers, would rise just 5.5 inches; the Arctic ice would shrink another quarter but no more; temperature would rise a degree above current levels, and the worldwide precipitation changes would be half as severe.

The research will be published next week in the journal Geophysical Research Letters.

The 70 percent cut scenario would stabilize concentrations of the heat-trapping gas carbon dioxide in the atmosphere at 450 parts per million by the end of this century. The U.S. government views reductions to this level as an attainable, albeit aggressive, goal.

Some climate scientists, including NASA’s James Hansen, have said concentrations of 350 parts per million are required to avoid runaway global warming. Hitting that mark has become the rallying cry for a campaign called Today’s level is more than 385 parts per million.

Given the current pace of global greenhouse emissions, aggressive cuts that curb future warming may prove difficult, according to a poll released by The Guardian on April 14:

Almost nine out of 10 climate scientists do not believe political efforts to restrict global warming to 2C will succeed, a Guardian poll reveals today. An average rise of 4-5C by the end of this century is more likely, they say, given soaring carbon emissions and political constraints.

Such a change would disrupt food and water supplies, exterminate thousands of species of plants and animals and trigger massive sea level rises that would swamp the homes of hundreds of millions of people.

So, we appear headed for a warmer climate, perhaps unlike anything we’ve experienced. Will civilization as we know it survive the change? Alex Steffen at framed it this way in his April 6 Save the Holocene! post:

The reality is that modern humanity and human civilization are the fruit of a very tightly banded set of interconnected climate and biological conditions. We need a certain kind of world in order to thrive, and that world is essentially the mild, moderately wet, biologically abundant world of the Holocene. We’ve never left that world, and in fact we are still intimately dependent on its plenty for our very survival.