With global warming, expect rainfall changes

Don't expect the weather patterns you remember from when you were a kid to persist.

Increasing global temperatures are, and will continue, to alter the world's water cycles, Susan Solomon, senior scientist at the National Oceanic and Atmospheric Administration (and the co-chair of the latest report from the Intergovernmental Panel on Climate Change) told attendees at the American Association for the Advancement of Science taking place in San Francisco.

"The places that are wet are going to get wetter, and the places that are dry are going to get drier," she said. In particular, that means that Spain, Mexico and the Sahel region that crosses Northern Africa will see less rainfall, while Norway will likely see more. The 2003 heat wave that killed thousands in Europe can be seen as a precursor to future climate change effects, she said.

These prospective changes in rainfall also make her a skeptic of plans, proposed by some, to combat global warming by inserting particles into the atmosphere to reflect sunlight. The idea is to reduce the amount of sunlight that strikes the Earth and thereby lower temperatures.

A layer of man-made reflecting particles, however, could easily disrupt the normal evaporation and rainfall cycles, and potentially make the planet more boggy.

"Changes in rainfall are tied to temperature changes and the amount of light hitting the earth," she said, adding that these sorts of plans "really worry me."

The changes in precipitation patterns and rainfall were one of the more significant elements of the fourth IPCC report, she said. Scientists, policy makers and the public are looking at more than just temperature changes when it comes to global warming. Instead, they are examining the Earth as an entire system and studying the consequences of what happens when the planet warms.

She also says she's been pleasantly surprised by the reaction to the latest report, which came out earlier this year, and scientific studies of global warming in general. "I've met a number of Congressmen who've said 'I've gone from being a skeptic to being a believer,'" she said. People she meets randomly in airports also seemed fairly well versed on the subject.

Solomon also reiterated many of the findings of the report, and they aren't pretty. Global warming is unequivocally occurring, she said. The Earth is about 0.75 degrees Celsius, or one degree Fahrenheit, warmer than it was in 1860.

There is also a 90 percent probability that the rise in temperatures comes from greenhouse gases emitted through pollution and human activity. Multiple points bear this out. For instance, 19 of the 20 warmest temperatures on record have occurred in the last few decades.

"Something unusual is going on," she said. "This is not random."

Some researchers have also examined what would have happened had humans not spewed carbon dioxide into the atmosphere. Because of volcanoes such as Mount Pinatubo, the temperature globally should have dipped slightly over the century. (Volcanoes emit particles and thus lower temperatures.).

Right now, the concentration of CO2 in the atmosphere is about 400 parts per million. If it goes to 600 parts per million, global average temperatures could rise 1.8 to 2.9 degrees Celsius by 2100. If CO2 rises to 1500 parts per million, it could rise to between 2.4 and 6.4 degrees Celsius. In any event, even if greenhouse gases induced by human behavior were capped today, we'd still see rising average temperatures over the next few decades.