Near Certainty: Humans Are Behind a Warming Planet

A leaked draft report by the Intergovernmental Panel on Climate Change (IPCC), an international group of hundreds of scientists, 195 governments, and more than 100 non-governmental organizations, further increases the certainty that climate change is man-made. According to BBC News, the report will say these global experts are now “95 percent certain that our use of fossil fuels is the main reason behind the global rise in temperatures since the 1950s.” The report will also update the IPCC’s direst forecasts, contending that sea levels could rise by 3 feet by 2100 if nothing is done to limit carbon dioxide and other greenhouse gases in the atmosphere. The 5th assessment report of the IPCC is the first major report by the U.N. group since 2007.

The reports are highly influential. The New York Times writes: “Hundreds of billions of dollars are being spent on efforts to reduce greenhouse emissions, for instance, largely on the basis of the group’s findings.”

Over the years, the groups has become more and confident that humans are behind climate change. While the 2007 report was certain that the climate was warming, it punted on assigning responsibility, arguing that odds were 90 percent that human activities caused climate change. “The language in the new draft is stronger, saying the odds are at least 95 percent that humans are the principal cause.”

On how much temperatures could increase if carbon dioxide levels in the atmosphere doubled, this new report will argue that the rise could be “as low as 2.7 degrees Fahreneheit.” This is a lower low-end estimate. The 2007 report “largely ruled out any number below 3.6 degrees Fahrenheit.” Some scientists argue that the IPCC is now being too conservative with its new estimates.

BBC News says the panel will also try to explain why temperatures have been rising more slowly since 1998, ” a controversial slowdown” that doesn’t seem to jive with the broader trends. “According to the leak, they will put it down to natural meteorological variations and other factors that could include greater absorption of heat into the deep oceans – and the possibility that the climate is less sensitive to carbon dioxide than had previously been believed.”

On sea level rise, there is also a range of numbers, depending on whether governments get emissions under control. If they can, sea level rise could be “as little as 10 inches by the end of the century. That is a bit more than the eight-inch increase in the 20th century, which proved manageable, even though it caused severe erosion along the world’s shorelines.” On the other hand, if nothing is done, sea levels could rise by 3-feet, presenting major threats for the hundreds of millions who live on coasts.

The Guardian
writes that the report will end up being quite similar to the last one released in 2007. “There will be slight changes to our confidence in certain observations. Climate models will have improved slightly, particularly in how they handle atmospheric particulates and cloud formation. A major effort since the last report has been the use of climate models to predict changes at the regional level. The report will likely say that this endeavor has had mixed success.”

But some major events in the past 5 years are expected to get more attention. In the 4th assessment report in 2007, “ice loss, particularly from Greenland, was a minor issue. Now, it is clear that not only Greenland, but also Antarctica are melting and this melt is raising sea levels. Furthermore, Arctic sea ice is being lost faster than previously reported.”

There are still many areas where the world’s great climate scientists still disagree. According to The Guardian, debate is still on-going on how hurricanes will change in a warming world — “the most powerful hurricanes are becoming even more powerful, but the change in frequency is not known.” Furthermore, while extreme weather has increased, what will be the changes to tornadoes and thunderstorms?

IPCC spokespeople argue that the report is bound to further change so it’s best not to put too much into the leaks. In fact, the 15-page executive summary, which is expected to be ready in mid-September, has already received 1,800 comments and counting.

Image credit: (1) Coney Island, New York City, Heat Wave /, (2) Coastal Erosion, Norfolk, UK / FREdome Visionary Trust

One thought on “Near Certainty: Humans Are Behind a Warming Planet

  1. Jim Somers 08/21/2013 / 2:18 pm

    The IPCC has been full of leaks for years

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