Humans are Causing Global Warming & it is Already Impacting Us: four key take-aways from the IPCC

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This morning, the climate science community released its latest consensus report. More than 600 researchers from 32 countries reviewed more than 9,000 peer-reviewed studies for this report compiled by the Intergovernmental Panel on Climate Change and signed-off by governments around the world. It is the definitive scientific consensus on the state of climate change science.  The findings of this new report are clear: humans are causing climate change, we are already beginning to see the changes caused by climate change, the impacts are accelerating, and we can do something about if we act boldly.

The report –the Summary for Policymakers on the “Physical Science Basis”—from the Intergovernmental Panel on Climate Change (IPCC) is the first of a series of reports in its fifth round of “Assessment Reports” – often referred to as AR5. This summary is based on the findings elaborated in over 2000 pages of separate chapters based upon the findings in 9,200 peer-reviewed articles. It is a robust document, heavily scrutinized by leading scientists around the world, and based upon “peer-reviewed” articles that go through their own heavy scrutiny before they are published.

Here are (at least) four key findings:

Take-Away #1: Scientists are more certain than ever that humans are causing climate change, through carbon pollution.

For more than two-decades scientists around the world have concluded with greater and greater confidence that humans are causing climate change. And with this report scientists are now even more confident – more than 95% confident that humans are causing climate change. As the report states:

“Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.”

Take-away #2: We are seeing climate change right now.

The United States is already paying a heavy price for climate change – with $140 billion in damages last year from crop losses, wildfires and severe storms. Arctic sea ice melted last year to its lowest level since we began measuring it with satellite images in 1978. As the report states:

“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”

People around the world already feeling the impacts of these changes. You don’t have to take it from me, but listen to the interviews from a fifth generation farmer from Iowa, a witness to the wildfires in California, a bison rancher and beekeeper suffering from drought in Texas, a resident of New York who incurred property damage from Hurricanes Sandy and Irene, and a minister who witnessed the flooding from Hurricane Katrina.

Take-away #3: The impacts are accelerating.

As we pump more global warming pollution into the atmosphere, the climate system is responding. Temperatures are increasing, sea levels are rising, ice sheets are melting, and more. And many of these changes are accelerating as the report notes:

“Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850”

“The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence).”

In the lead up to the release of this report a handful of organizations and individuals, some with ties to the fossil fuel industry, have tried to make hay out of an apparent slowdown in the rate of global surface temperature increases in recent years. Don’t be misled, and don’t be distracted as my colleague notes.

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Take-away #4: We can avoid catastrophic change if we take bold and decisive action now.

Business as usual isn’t acceptable. The report notes that failure to act will lead to temperature increases that are way beyond acceptable. The IPCC doesn’t issue a “threat” warning as that isn’t their mandate. They are asked by governments to present the facts on climate change. But, one look at what the report details and you can see that the time for bold and urgent action is right now. As the report states:

“Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.”

As researchers at the World Resources Institute (WRI) point out, the IPCC report documents how we have already burned through 53 percent of our carbon budget associated with having likely chance of limiting warming to 2°C (3.6°F). And as WRI notes: "We may have just about 30 years left until the world’s carbon budget is spent if we want a likely chance of limiting warming to 2 degrees C".

We can turn the corner on this trend as we take urgent steps to put limits on carbon pollution, deploy more clean energy, address deforestation, and clean up our transportation system. The numbers are daunting, but they must not lead us to throw-up our hands and give up.  

The message from the IPCC report is clear – the time for debate is over and the time for action is urgent.


Photo with IPCC quotes added: sun over power plant, courtesy of Sir Mildred Pierce. Climate Witnesses video: interviews with witnesses at the Congressional Safe Climate Caucus Forum on the Impacts of Climate Change, Sept. 17, 2013. Sea-ice melt: The Global Call for Climate Action.