US gov’t releases major new climate change report

A few months ago, there were fears the US’s famously anti-science current administration might censor a major multi-agency climate report reaffirming the reality of global warming before it could be published. Yet reason has prevailed, somewhat incredibly, and the 2017 Climate Science Special Report has been published. It confirms everything we already knew: the Earth is warming fast and it’s all our fault.

It is “extremely likely” that humans are driving warming on Earth since the 1950s. That statement — which indicates a 95 to 100 percent confidence in the finding — came in a report released November 3 by the U.S. Global Change Research Program. This interagency effort was established in 1989 by presidential initiative to help inform national science policy.

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The last national climate assessment, released in 2014, also concluded that recent warming was mostly due to humans, but didn’t give a confidence level (SN Online: 5/6/14). Things haven’t gotten better. Ice sheet melting has accelerated, the 2017 report finds. As a result, projections of possible average global sea level rise by 2100 under a high greenhouse gas emissions scenario (in which emissions rise unabated throughout the 21st century) have increased from 2 meters to as much as 2.6 meters.

In addition, the report notes that three of the warmest years on record — 2014, 2015 and 2016 — occurred since the last report was released; those years also had record-low sea ice extent in the Arctic Ocean in the summer.

The entire report is available online. The executive summary doesn’t mince any words:

Global annually averaged surface air temperature has increased by about 1.8°F (1.0°C) over the last 115 years (1901–2016). This period is now the warmest in the history of modern civilization. The last few years have also seen record-breaking, climate-related weather extremes, and the last three years have been the warmest years on record for the globe. These trends are expected to continue over climate timescales.

This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.

In addition to warming, many other aspects of global climate are changing, primarily in response to human activities. Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.

It doesn’t get any better from there: rising sea levels that trigger more floods, worsening storms that wreak more destruction, more frequent heatwaves, forest fires and droughts that destabilize the ecology and the human industries that rely on it … and those are all events we’re witnessing right now. We’re sentencing our environment to death by a thousand cuts, and all our awareness and mounting efforts won’t amount to anything unless governments decide to start playing hardball.

Have I mentioned that the current administrator of the US’s Environmental Protection Agency doesn’t believe carbon dioxide is driving global warming, and that the sitting president once said it was all a Chinese hoax?

(via @adamconover)