A Warming World

Global warming has already led to rising sea levels and dramatic increases in temperature in the Arctic, and scientists warned Friday that its effects will hit closer to home, creating heat waves, droughts and hurricanes.

How bad it gets, say international scientists in the latest release of findings on climate change, depends on what actions people and nations take to reduce the burning of fossil fuels, the destruction of forests and everyday activities that emit carbon dioxide and other greenhouse gases into the air.

In the United States, the West will be hardest hit, scientists say. Heat waves, droughts and intense hurricanes are likely to increase in the coming decades. Air temperatures in the Southwest, particularly from California to Texas, are projected to rise in the summer about 10 degrees by the end of the century, assuming there is a moderate increase in greenhouse gas emissions. A reduction in emissions might keep the temperature rise to 5 degrees.

The findings were released in Paris as part of the fourth assessment by the Intergovernmental Panel on Climate Change, or the IPCC, formed by the United Nations. It is the result of six years of work and is built on a previous dozen years of study by hundreds of researchers from more than 100 nations.

In a warming world, the Southwest will receive less rain, and the Pacific Northwest may get more, although that is less certain, scientists say. And even less clear is what will happen in Northern California, where the unpredictability of El Niños, ocean winds and currents make forecasting difficult.

Over the next several decades, the snow season is expected to shorten across North America, and the snow cover is expected to contract. Permafrost will thaw to greater depths, the scientists project. And the East Coast will be wetter and cloudier.

from the San Francisco Chronicle