Is the damage from climate change now irreversible?

Our planet may now be committed to some damaging and irreversible impacts as a result of the greenhouse gases already in the atmosphere. The rise in the globe’s temperature by the end of the century may be nearly double what scientists and policymakers have identified as the upper limit of warming the world can afford in order to avert catastrophic climate change. This from a report by the Intergovernmental Panel of Climate Change (IPCC) released by the United Nations Environment Program. Juliet Eilperin has this in today’s Washington Post:

Climate researchers now predict the planet will warm by 6.3 degrees Fahrenheit by the end of the century even if the world's leaders fulfill their most ambitious climate pledges, a much faster and broader scale of change than forecast just two years ago, according to a report released Thursday by the United Nations Environment Program.

The new overview of global warming research, aimed at marshaling political support for a new international climate pact by the end of the year, highlights the extent to which recent scientific assessments have outstripped the predictions issued by the Nobel Prize-winning U.N. Intergovernmental Panel on Climate Change in 2007.

Robert Corell, who chairs the Climate Action Initiative and reviewed the UNEP report's scientific findings, said the significant global temperature rise is likely to occur even if industrialized and developed countries enact every climate policy they have proposed at this point. The increase is nearly double what scientists and world policymakers have identified as the upper limit of warming the world can afford in order to avert catastrophic climate change.

"We don't want to go there," said Corell, who collaborated with climate researchers at the Vermont-based Sustainability Institute, Massachusetts-based Ventana Systems and the Massachusetts Institute of Technology to do the analysis. The team has revised its estimates since the U.N. report went to press and has posted the most recent figures at ClimateInteractive.org.

The group took the upper-range targets of nearly 200 nations' climate policies -- including U.S. cuts that would reduce domestic emissions 73 percent from 2005 levels by 2050, along with the European Union's pledge to reduce its emissions 80 percent from 1990 levels by 2050 --and found that even under that optimistic scenario, the average global temperature is likely to warm by 6.3 degrees.

World leaders at the July Group of 20 summit in L'Aquila, Italy, pledged in a joint statement that they would adopt policies to prevent global temperature from climbing more than 2 degrees Celsius, or 3.6 degrees Fahrenheit: "We recognize the broad scientific view that the increase in global average temperature above pre-industrial levels ought not to exceed two degrees C."

Corell, who has shared these findings with the Obama administration as well as climate policymakers in China, noted that global carbon emissions are still rising. "It's accelerating," he said. "We're not going in the right direction."

Achim Steiner, UNEP's executive director, told reporters at the National Press Club on Thursday that the report aims to update the IPCC's 2007 findings to reflect both new physical evidence and a more sophisticated understanding of how Earth systems work.

"With every day that passes, the underlying trends that science has provided is . . . of such a dramatic nature that shying away from a major agreement in Copenhagen will probably be unforgivable if you look back in history at this moment," Steiner said. He noted that since 2000 alone, the average rate of melting at 30 glaciers in nine mountain ranges has doubled compared with the rate during the previous two decades.

"These are not things that are in dispute in terms of data," he said. "They are actually physically measurable."

Other findings include the fact that sea level might rise by as much as six feet by 2100 instead of 1.5 feet, as the IPCC had projected, and the Arctic may experience a sea-ice summer by 2030, rather than by the end of the century.

The UN press release has further details:

Researchers have become increasingly concerned about ocean acidification linked with the absorption of carbon dioxide in seawater and the impact on shellfish and coral reefs.

Water that can corrode a shell-making substance called aragonite is already welling up along the California coast decades earlier than existing models predict.

Losses from glaciers, ice-sheets and the Polar Regions appear to be happening faster than anticipated, with the Greenland ice sheet, for example, recently seeing melting some 60 percent higher than the previous record of 1998.

Some scientists are now warning that sea levels could rise by up to two metres by 2100 and five to ten times that over following centuries.

There is also growing concern among some scientists that thresholds or tipping points may now be reached in a matter of years or a few decades including dramatic changes to the Indian sub-continent's monsoon, the Sahara and West Africa monsoons, and climate systems affecting a critical ecosystem like the Amazon rainforest.

The report also underlines concern by scientists that the planet is now committed to some damaging and irreversible impacts as a result of the greenhouse gases already in the atmosphere.

Losses of tropical and temperate mountain glaciers affecting perhaps 20 percent to 25 percent of the human population in terms of drinking water, irrigation and hydro-power.

Shifts in the hydrological cycle resulting in the disappearance of regional climates with related losses of ecosystems, species and the spread of drylands northwards and southwards away from the equator.

Recent science suggests that it may still be possible to avoid the most catastrophic impacts of climate change. However, this will only happen if there is immediate, cohesive and decisive action to both cut emissions and assist vulnerable countries adapt.

The UN has already released a citing a growing frequency and intensity of climate-related natural disasters around the world that drove more people from their homes last year than conflicts. The Obama administration is pressing this week for an end to fossil-fuel subsidies as part of the current G-20 summit in Pittsburgh. That's good but a far more aggressive approach will be needed to preserve a livable planet.