- A leaked new government report that’s part of the National Climate Assessment provides an updated look at what we know about climate change. It says the world is significantly warmer than it used to be and getting hotter, mostly because of human activity. The Trump administration needs to sign off on the report before it’s officially released.
The world is warmer than it would be without human activity and it’s continuing to get warmer.
We, as people, are mostly responsible for that. And it’s going to get worse – much worse, if we don’t take significant action on greenhouse gas emissions.
That’s the essential takeaway from the leaked draft of a major new report on the state of the climate, which The New York Times published in full (previous versions of the report had been available, though not the latest version released by The Times). Scientists from 13 different federal agencies – including the National Oceanic and Atmospheric Organization (NOAA), the Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the Department of Defense (DOD) – contributed to the report, which is supposed to be part of the congressionally-mandated National Climate Assessment.
The National Science Foundation (NSF) has signed off on the report. But before the report is officially released, the Trump administration – including EPA head Scott Pruitt, who disagrees with the scientific consensus about what’s happening with the climate and doesn’t believe carbon dioxide (CO2) contributes to warming – needs to sign off on it too.
Because of that, researchers told The Times that they fear the report could be suppressed or changed. (Presumably, that’s why it was leaked to the Times in its NSF-approved form.)
Below, we’ve selected key findings from the 545-page report.
- REUTERS/Corey Hardcastle/Handout via Reuters
What government scientists say is happening with the climate
- From 1865 to 2015, the global average surface temperatures became about 1.6 degrees Fahrenheit (.9 degrees Celsius) warmer. This can be seen in measurements of surface, atmospheric, and oceanic temperatures; melting glaciers; disappearing snow cover; shrinking sea ice; rising sea level; and more atmospheric water vapor. This can be said with “very high confidence,” meaning that there’s high consensus, strong evidence, and that this is well documented. With similar levels of confidence we can say that human activities, especially greenhouse gas emissions (largely the result of burning fossil fuels), are responsible for this warming. The authors wrote: “There are no alternative explanations, and no natural cycles are found in the observational record that can explain the observed changes in climate.” We can say with 95-100% certainty that humans caused most of the global temperature increase seen since 1951. While natural variability from effects like El Niño exists, that variability only plays an important role on short time scales, not with larger climate trends. Gases that we’ve already emitted will continue to warm the world, meaning that more warming is already baked into the system, making it harder and harder to avoid levels of warming considered dangerous. The authors wrote that even if the world stopped emitting gases today, we could expect at least an additional .3 degrees C of warming. In the near term, the US can expect to see temperature increases of at least 1.4 degrees C over the next few decades (higher than the global average). That’s pretty severe and could lead to more extreme heat waves, which kill more people than any other kind of extreme weather event. Record-setting temperatures of recent years will become common. With very high confidence, we can expect the frequency and intensity of weather extremes like heavy precipitation and extreme heat to continue to rise. For events like severe storms and droughts, the trends vary by region. There’s strong evidence and consensus that oceans are absorbing more than 90% of the heat being trapped inside the climate system, which means that they are taking in CO2. There’s suggestive evidence that because of this, they are becoming more acidic faster than at any point in at least the past 66 million years. Increased acidity can devastate marine life, especially coral reefs, which cover less than 2% of the ocean floor but are depended on by about 25% of marine species – including many key food sources for humans. Temperatures in Alaska and the Arctic are rising more than twice as fast as the global average temperature rise, something that can be seen in ice loss at the North Pole. There could be unanticipated tipping points we are approaching, caused by severely diminished ice sheets or severe extreme weather events. Since the last National Climate Assessment, we’ve become significantly better at being able to attribute human influence to individual extreme weather and climate events, some of which are identified in the report. There was no “global warming hiatus” between 2000 and 2013 and the planet has continue to warm at a steady pace as predicted.
Perhaps most importantly, some predictions show that there’s hope human action could make a difference:
- The authors wrote that there’s “high confidence” that by later this century, US temperatures will be 2.8 degrees C warmer on a low emission scenario and 4.8 degrees C warmer on a high emissions scenario. While there’s high confidence that at least 1 foot of sea level rise can be expected by the end of the century, different emissions scenarios could lead to vastly different levels. There’s inconclusive evidence that at present we could still see a 4 foot sea level rise; but under a high emissions scenario the authors wrote that 8 feet cannot be ruled out. There’s high confidence that we haven’t slowed down emissions enough to stabilize the climate to the goals set by the Paris Agreement. Even under a mid-to-low emissions scenario, we’ll have emitted enough to pass 2 degrees C in warming by some point between 2051 and 2065.
Quite simply, climate change is real and the longer we wait in trying to slow emissions, the worse the consequences will be.