STOCKHOLM – Top scientists have a better idea of how global warming will shape the 21st century: In a new report, they predict sea levels will be much higher than previously thought and pinpoint how dangerously hot its likely to get.
In its most strongly worded report yet, an international climate panel said it was more confident than ever that global warming is a man-made problem and likely to get worse. The report was welcomed by the Obama administration and environmental advocates who said it made a strong and urgent case for government action, while skeptics scoffed at it.
There is something in this report to worry everyone, said Chris Field, a Carnegie Institution scientist who is a leader of the Intergovernmental Panel on Climate Change but wasnt involved in the report released Friday.
Without major changes, he said, the world is now on track for summers at the end of the century that are hotter than current records, sea levels that are much higher, deluges that are stronger and more severe droughts.
The Nobel Prize-winning panels report called the warming of the planet since 1950 unequivocal and unprecedented and blamed increases in heat-trapping greenhouse gases such as carbon dioxide from the burning of coal, oil and gas.
The United Nations created the panel of climate researchers in 1990 to tell world leaders what science is saying about global warming and how bad it will get. This is the groups fifth major state-of-the-science report, approved by nearly 200 nations at the end of a weeklong meeting in Stockholm.
The panel fine-tuned its predictions. Its worst-case scenario had put the sea level increase at just shy of 2 feet by 2100; now its slightly more than 3 feet. They cite better understanding of how much glaciers and ice sheets are melting and how water expands as it warms.
Unless the world drastically cuts emissions – an event that scientists called highly unlikely to happen – the panel said Earth will warm by at least 2 more degrees this century in all but one of the four scenarios they outline.
That 2-degree threshold is where the risks start piling up, including food crises in developing countries, people forced to move from coastal cities because of rising seas and more extinctions, said Princeton University climate scientist Michael Oppenheimer, a co-author of a report on climate change. This is a point where any sensible person would look and say the risks are just getting too high.
One of the most contentious issues was how to deal in the report with what appears to be a slowdown in warming based on temperature data for the past 15 years.
The IPCC made only a brief mention of the issue in Fridays summary for policymakers, stressing that short-term records are sensitive to natural variability and dont in general reflect long-term trends.