UN scientists tell us, ready or not, here comes climate change

Get ready, 'cause here it comes.

That's one way to summarize the latest message from the world's largest group of climate change scientists.

A new report from the UN's Intergovernmental Panel on Climate Change is out and makes it clearer than ever that global warming is already changing the world and affecting our lives, and that the impacts are only going to get worse. The report contains a litany of sobering impacts, from too much water some places, to too little water elsewhere, shifting disease risks, failing infrastructure and food shortages.

"Nobody on this planet is going to be untouched by the impacts of climate change,” said IPCC chair Rajendra Pachauri in Yokahama, Japan, where the report was released on Monday.

And Pachauri says the consequences could be immense. “The very social stability of human systems could be at stake,” he declared.

The new report is the second part of a three part review of climate science and related issues released every few years by a huge group of scientists from around the world who make up the IPCC. The organization won the Nobel Peace Prize after its last report was released in 2007.

Volume one of its Fifth Assessment Report, released last fall, reviewed the basic science, and established more clearly than ever that climate change is happening, that humans are largely responsible and that it's going to trigger sweeping global changes for centuries into the future.

Volume three, which will examine technological and other options for limiting climate change, is due out in April.

Volume two, released this week, looks at the impact climate change is already having and likely will have in the future, how vulnerable societies are to those changes, and how societies might adapt to them.

The report outlines significant changes already underway, including:

• Water supplies being increased or decreased based on changes in precipitation and melting snow and ice.
• Terrestrial and aquatic ecosystems being altered, with potentially big impacts on human communities.
• Agriculture being hurt by temperatures changes and changes in water availability, though there will be some improvements.

The report also found that climate change is already making existing economic and social problems worse, especially for the world’s poor.

Looking ahead, the report identifies eight key risks that it says are almost certain to kick in, including:

• Widespread risk of illness and death from flooding and heat waves.
• High risk of breakdown of critical infrastructure from extreme weather events.
• High risk to food security and access to water.

It also found that many regions are ill-equipped to cope with these sorts of events.

But the report is not without its silver lining. As is common in such reports, it makes clear that we're not locked into a worst-case scenario, and that how bad things get is largely dependent on how seriously the world takes the problem and what changes it makes to address it.

There was a flicker of dissent within the group of scientists, though. One of the roughly 750 authors had his name taken off the report because he felt its projections on impacts were “too alarmist.”

Panel Vice Chair Jean-Pascal van Ypersele responded to the criticism by saying "it's because the facts and the science and the data show that there are reasons to be alarmed."

Note: This report reflects a correction from the original broadcast version. The IPCC's AR 5 Working Group II report has roughly 750 (745) authors and editors, not 1,500, along with 1,729 expert and government reviewers.