Global warming is real. It’s already begun, and it’s accelerating.

Temperatures measured around the world show that 11 of the past 12 years have been the warmest since records were first kept, in 1850.

In the Pacific Northwest, the warmest 20-year period from 1930 to 2005 were the years 1986 to 2005. The warmest 10-year period was 1996 to 2005. The warmest five-year period? That would be 2001 to 2005.

Scientists have discerned at least a likely connection between certain human influences on the atmosphere and rising sea levels and the increasing number of heatwaves, droughts and hurricanes.

All of this is the consensus of the Intergovernmental Panel on Climate Change — this year’s recipient of the Nobel Peace Prize for the work on global warming the group started in 1988. The climate panel, which received input from more than 2,500 scientists in more than 130 countries, announced early this year that observations of higher temperatures worldwide since the mid-1900s are “very likely” caused by human activities, most prominently fossil-fuel burning.

By “very likely,” the scientists mean the odds are better than 90 percent that global warming is the direct result of humans pumping carbon dioxide and other greenhouse gases into the atmosphere, from fossil-fuel combustion, deforestation and farming practices.

This insight came in part from comparing current levels of carbon dioxide with those found in bubbles trapped in ice cores from the past 10,000 years.

The ice cores reveal that from the dawn of civilization until about 1750, the amount of carbon dioxide in the atmosphere fluctuated only slightly, between 260 and 280 parts per million, or less then .03 percent of the total atmosphere.

In the mid-18th century, societies learned how to burn coal for energy. Then came oil and natural gas. Combustion of these carbon-based materials creates carbon dioxide, and the amount of that gas in the atmosphere has risen to 379 parts per million.

In the worst-case global change scenarios that scientists have considered, that figure would approach 1,000 parts per million, or almost four times pre-industrial levels, by 2100.

Carbon dioxide and other greenhouse gases are so named because they trap the heat that Earth is radiating into space and send it back to Earth’s surface. Not that this is a bad thing. Greenhouse gases provide twice as much heating at the surface of the Earth than the sun. Without them, Earth wouldn’t be livable.

But as mounting and sometimes dramatic evidence has shown, much depends on the temperature staying more or less within the bounds familiar to our rapidly growing economy and population.

Changes under way

Temperatures have risen as a result of greenhouse gas pollution by 1.2 degrees Fahrenheit over the last 50 years, scientists believe. In tandem with this increase, water supplies are being threatened by diminishing snowpacks and increasing drought.

Growing seasons are changing. Seaside communities worry about rising sea levels. The oceans have already risen between 4.7 and 8.7 inches over the course of the 20th century, according to the best data available.

The glaciers of the North Cascade Mountain Range are rapidly shrinking. Even more dramatically — and ironically — Montana’s Glacier National Park has lost 124 of its 150 glaciers, according to reports, and the park might have none of its namesake attractions by 2030.

Carbon levels in the atmosphere continue to increase despite efforts at restraint in Europe and the United States.

Fossil-fuel combustion put 23.5 billion metric tons of carbon dioxide into the air annually in the 1990s. This has increased to 26.4 billion metric tons every year on average from 2000 to 2005, according to the climate panel.

Much of the recent gains can be attributed to China. A study by the Netherlands Environmental Assessment Agency released earlier this year said China eclipsed the United States in 2006 as the top carbon emitter in the world, putting out 6.2 billion metric tons of carbon dioxide that year compared with 5.8 billion from the U.S.

U.S. carbon emissions decreased 1.4 percent in 2006 compared with the previous year, the Netherlands report said. In the European Union, carbon output remained unchanged from 2005 to 2006, according to the report. Meanwhile, China’s output increased 8.7 percent from 2005 to 2006.

Carbon dioxide is not the only major greenhouse gas, but it does most of the warming. The climate panel figures that carbon dioxide does about twice as much work as the other three major greenhouse gases combined. The other gases are methane, nitrous oxide and the halocarbons, many of which are manmade and used in solvents, pesticides, refrigerants and plastics.

Future forecast

By the end of this century, temperatures will increase anywhere from 2 to 11.5 degrees Fahrenheit, according to the climate panel. To come up with this range, the group plugged six different socio-economic scenarios into computer climate models. Some scenarios were more environmentally friendly. Others assumed more aggressive economic growth.

The inertia behind global warming is strong. If humans figured out how to stop increasing the amount of greenhouse gases in the atmosphere by 2100, the average global temperature still would go up almost another degree by 2200. Sea levels would continue to rise for several centuries. If global warming were sustained over thousands of years, the Greenland ice sheet would melt and sea level would rise by 23 feet, roughly the figure Al Gore quotes in “An Inconvenient Truth.”

For the most part, scientists don’t look that far ahead. They focus a lot of their work on the next 40 years because policy decisions don’t apply much farther ahead than that, and there’s too much uncertainty in computer model runs and in the changes that may happen in the next few decades.

Skagit Warming Series:
Skagit Warming Page
Temperatures rising, glaciers melting in Northwest
Nature’s Laboratory
Researchers explore effects of climate change on health
Warming’s impact on Skagit water
Climate change poses threat to regional icons
Warming shifts odds away from salmon survival
Climate change could have dramatic impact on local agricultural scene
Cashing in on global warming
Warming: A rising tide
Tribe, La Conner on front lines
Green Power
Nuclear power unlikely alternative
Skagit Warming: Government action
Climate and You
What You Can Do
Why turn off the lights?
Skagit Warming: Tell us what you think

* Ralph Schwartz can be reached at 360-416-2138 or .