Problematic
predictions
Temperatures over the past decade have given no solace
to the once-vocal skeptics of global warming. Indeed, warming has accelerated
rapidly since 1990. Kevin Trenberth, a climatologist who helped write
the 2001 IPCC report, says, "It certainly has continued to warm. 1998
was the warmest year on record, and 2001 was the second-warmest. The 1990s
were the warmest decade in the last 1,000 years."
No matter how you cut it, temps are expected to
rise fast. Economic and technological choices affect the outcome: A1B
and similar gibberish refer to different scenarios for the pace and type
of future economic and technological development. Greener living can produce
a cooler planet. SRES = IPCC Special Report on Emissions Scenarios. "IS92"
methods used an older estimate of total greenhouse emissions.
IPCC, p. 70.
Overall, the warming has amounted to 1.2 degrees F over the past century. The IPCC says that's mainly due to human activity.
The predictions are even more ominous. According to the IPCC, surface temperatures in 2100 will be 1.4 to 5.8 degrees C warmer than 1990.
The predictions of a decade ago were alarming enough, but these are significantly hotter. But why trust a climate prediction for 50 or 100 years down the line when meteorologists can't even predict the weather half the time...?
Erratic eruption
Since the start of the global warming debate, climatologists
have stressed the extraordinary complexity of climate prediction. Early
computer climate models were primitive representations of atmospheric
conditions. Today's climate models use stronger computers and slicker
software to factor in some of the hydrology, geology and biology that
influence climate.
Who's the gassiest? America, that's who! *FSU =
Former Soviet Union. EPA.
As new factors arise, they are entered into the climate equation, as you can see from the case of the airborne aerosols. "At the beginning of the 1990s, the forecasts were right on track," says Schneider, with almost constant warming.
Then, in 1992, a sudden cooling started. Climatologists
soon realized that Mt Pinatubo in the Philippines, in the largest eruption
of the 20th century, had spewed a gazillion tons of aerosols into the
atmosphere.
These tiny particles reflected sunlight back to space, reducing heat input
to the planet and temporarily slackening the greenhouse effect When the
early global warming models, which did not account for cooling caused
by aerosols (which are also produced by burning coal and oil), were changed,
the new models have forecast average temperatures "right on the nose,"
says Schneider.
As we'll see, that's not proof that human activities have caused global warming, but it sure is suggestive.
High seas rising. Coming soon to a shoreline near you?
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