What you need to know about climate change
President Trump's decision to pull out of the global Paris climate agreement — joining Syria and Nicaragua as the only countries not in the pact — will signal to the world that his administration does not view climate change as a significant concern.
Focus on this: Trump's call to withdraw might sway other countries around the globe, especially developing countries like India, to move away from an active position on combatting climate change.
There's consensus: Of the peer-reviewed climate science papers that take a position on climate change, more than 97% agree that it is real and likely caused by human activity. NASA has a collection of major scientific organizations that also endorse this position.
The scientific evidence, per NASA:
- Temperature: Earth's average surface temperature has risen by 2 degrees Fahrenheit since the late 1800s. And 16 of the 17 warmest years on record have taken place since 2001 — with 2016 as the warmest ever recorded.
- Sea level: Global sea levels rose by 0.19 meters during the period from 1901 to 2010, but the NOAA predicts a rise of 0.3 to 2.5 meters during this century alone. A rise of 0.35 meters would increase the risk of damaging and disruptive flooding by 25 times for major U.S. coastal cities — and that could happen by 2030.
- Sea ice: The extent of Arctic sea ice was at its lowest ever maximum this year, more than a half a million square miles below its long-term average.
- Glaciers: The World Glacial Monitoring Service said that "the rates of early 21st-century [glacial] mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history."
- Extreme weather: Since 1950 the United States has become more likely to see record high temperatures and less likely to see record low temperatures — all while extreme weather events like drought become more common.
- Ocean acidification: Carbon dioxide emitted into the air is absorbed by the oceans — as a result, the oceans' acidity has increased by 30 percent since the late 1800s — which harms coral reefs and other creatures that serve as the base of the sea's food web.
Why it matters:
Axios' Amy Harder summed it up in her analysis of the decision yesterday: "Trump's planned decision to withdraw from the deal will set the world back on an environmental issue nearly every other country realizes and acknowledges is a real problem in need of a global solution."