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
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
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.
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
- 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
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
- 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.
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