The Reckoning: Global Warming Is Likely to Cause Huge Climatic Changes-And Possibly a New Ice Age
Motavalli, Jim, E Magazine
What killed the saber-toothed tiger, the mastodon and the mammoth, formidable animals that were on top of the food chain in North America 20,000 years ago? Was it fierce Stone Age hunters as has commonly been assumed, or the little-studied but very real phenomenon of abrupt climate change?
This question is not just of academic interest, to be debated by pipe-smoking professors at conferences. The rapid natural climate changes at the end of the Ice Age could be mirrored by man-made global warming in the 21st century, leading to devastating consequences for the planet's biodiversity and the human race itself. As the Bush administration rebuffs international treaties and embarks on a leisurely and largely redundant 10-year study of global warming science, the evidence we have already amassed points to a climatic emergency, and a vastly changed Earth in 2100 and beyond. To avert that possibility, scientists say we'd need to reduce emissions of the most important greenhouse gas, carbon dioxide (CO2), from transportation and industry by 80 percent, a near impossibility given current political realities.
The Ice Evidence
While no scientists were available to record data 400,000 years ago, detailed studies of ancient ice, brought up in deep core samples, reveal that the level of CO2 has been steadily rising for the last 15,000 years, most dramatically since the industrial Revolution first began pumping large quantities of CO2 into the atmosphere. Recent surface temperatures are probably higher than at any time since the Middle Ages, Work at the University of East Anglia reveals the period from 1970 to 2000 as the Northern Hemisphere's warmest three decades in 1,000 years. Another study, cited in Coastal Heritage magazine, found that 80 percent of all species of plants and animals had made a climate-related shift in habitat.
Critics of global warming science point out that CO2 levels naturally rise and fall without human intervention. That's true, because there has been a steady 20 percent rise and fall over time from a mean of 240 parts per million (ppm). But today all indicators are going off the scale, and in only one direction. The current concentrations are higher than at any time in the last 400,000 years, according to data accumulated from the Vostok ice core in Antarctica.
But that's only the beginning. The influential Intergovernmental Panel on Climate Change (IPCC), composed of 2,500 climate scientists, envisions a series of scenarios for the end of this century. Like the United Nations' population projections, there are low, middle and high estimates, based on human activity.
Will we, finally, come together internationally and enforce a significant decrease in carbon emissions by 2100 to a modest 5.7 billion tons? Or will the world's ever-growing automobile and truck fleet, coupled with soaring human population and escalating energy needs, fulfill the IPCC's worst-case scenario, with five times that much CO2, 29 billion tons every year? The latter seems more likely, as energy demand in the Third World grows at 3.5 percent a year.
Britain's BBC reports that an annual emission of 29 gigatons of CO2 would mean "the mass death of forests, with the trees releasing the CO2 they had stored up, adding to global warming instead of restraining it. It would be likely to make the eventual collapse of the Ross Ice Shelf in Antarctica inevitable. That, in turn, could trigger a significant global sea-level rise, and the loss of huge and densely populated coastal areas."
Carbon dioxide levels in the atmosphere have risen 30 percent in the last century, but, again, that's only a beginning. Until 1999, two gigatons of CO2 were added to the atmosphere annually. Since then, with the addition of huge releases from large-scale forest fires, we've added six gigatons.
The lofty goals enunciated at the 1992 Earth Summit in Rio, to reduce CO2 to 1990 levels, have failed dismally. …