This is the scientific consensus on climate change

A new report clarifies the facts and urges Americans to take action

Published March 18, 2014 1:47PM (EDT)

How's this for a scientific consensus? The American Association for the Advancement of Science, the world’s largest general scientific society with a membership of 121,200 scientists and "science supporters" globally, just released an 18-page report confirming that the world is at growing risk of “abrupt, unpredictable and potentially irreversible changes” due to climate change.

It's called, simply, "What We Know," and the facts it presents follow three basic assertions (presented here as summarized by its authors):

1. The reality:

"Based on well-established evidence, about 97% of climate scientists have concluded that human-caused climate change is happening. This agreement is documented not just by a single study, but by a converging stream of evidence over the past two decades from surveys of scientists, content analyses of peer-reviewed studies, and public statements issued by virtually every membership organization of experts in this field. Average global temperature has increased by about 1.4˚ F over the last 100 years. Sea level is rising, and some types of extreme events – such as heat waves and heavy precipitation events – are happening more frequently. Recent scientific findings indicate that climate change is likely responsible for the increase in the intensity of many of these events in recent years."

2. The risks:

"Earth’s climate is on a path to warm beyond the range of what has been experienced over the past millions of years. The range of uncertainty for the warming along the current emissions path is wide enough to encompass massively disruptive consequences to societies and ecosystems: as global temperatures rise, there is a real risk, however small, that one or more critical parts of the Earth’s climate system will experience abrupt, unpredictable and potentially irreversible changes. Disturbingly, scientists do not know how much warming is required to trigger such changes to the climate system."

3. The response:

"Waiting to take action will inevitably increase costs, escalate risk, and foreclose options to address the risk. The CO2 we produce accumulates in Earth’s atmosphere for decades, centuries, and longer. It is not like pollution from smog or wastes in our lakes and rivers, where levels respond quickly to the effects of targeted policies. The effects of CO2 emissions cannot be reversed from one generation to the next until there is a large- scale, cost-effective way to scrub carbon dioxide from the atmosphere. Moreover, as emissions continue and warming increases, the risk increases."

None of the above, the scientists explained, is up for debate any longer. What's yet to be determined, however, is how many of those possibilities will come to pass, along with what we can and should do to mitigate the risks. In what the Guardian characterizes as a rare intervention into policy debate, the AAAS is hoping that making the scientific consensus as clear as possible, they can help advance the conversation to focus on the things we actually need to be debating right now. "Because so many people are confused about the science," the New York Times explains, "the nation has never really had a frank political discussion about the options."

“What’s extremely clear is that there’s a risk, a very significant risk,” Mario Molina, the head of the committee that produced the report, told the Times. “You don’t need 100 percent certainty for society to act.”

For more on the consensus, watch climate experts explain the facts below:

By Lindsay Abrams

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