A Global Science Experiment

The physics of climate change can be complicated to figure out because of all the different systems on earth: we know that greenhouse gases like carbon dioxide increase global temperatures by trapping heat from the sun, but how does that interact with the ocean, the plants, and so on? How do scientists validate their models when they predict that temperatures will rise when the CO2 level goes up, and so will sea levels?

The answer's pretty simple: historical data. From the Times:

From studying air bubbles trapped in Antarctic ice, scientists know that going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180 parts per million in the depths of ice ages to about 280 during the warm periods between. The evidence shows that global temperatures and CO2 levels are tightly linked.

For the entire period of human civilization, roughly 8,000 years, the carbon dioxide level was relatively stable near that upper bound. But the burning of fossil fuels has caused a 41 percent increase in the heat-trapping gas since the Industrial Revolution, a mere geological instant, and scientists say the climate is beginning to react, though they expect far larger changes in the future.

Indirect measurements suggest that the last time the carbon dioxide level was this high was at least three million years ago, during an epoch called the Pliocene. Geological research shows that the climate then was far warmer than today, the world’s ice caps were smaller, and the sea level might have been as much as 60 or 80 feet higher.

The concentration of CO2 is currently at about 400 parts per million. Before the Industrial Revolution, the concentration was 270 to 280 ppm. In just a few hundred years humanity has burned enough wood, gas, coal and oil to overpower all the natural CO2-absorbing mechanisms. We burn more than 20 billion tons of fossil fuels each year, and only half of that crap is absorbed naturally; the rest is still floating around in the air.

People frequently argue that people are "too small and insignificant" to change the planet's environment: but without even trying, we puny humans have increased the concentration of carbon dioxide across the entire globe by more than two-fifths in the time since the Declaration of Independence was signed.

If we continue on our current path, with China, India and other undeveloped countries increasing their use of fossil fuels as well, by 2100 we will increase CO2 levels to 900 ppm, more than three times the preindustrial level.

Some argue that historically, high CO2 levels were just a symptom of a warmer planet, and not the cause. We do know that there are cascading effects from a warming planet: CO2 and methane are escaping as the permafrost melts in the frozen tundra in Siberia, Alaska and the Yukon. But we also know the physics: as CO2 and methane levels increase, the greenhouse effect causes higher temperatures.

Once the temperature starts spiraling upward, it doesn't really matter what is cause and what is effect: adding more CO2 to the atmosphere is like throwing gasoline on a fire. If global warming isn't ultimately "our fault," it's especially important that we don't exacerbate the problem by tripling CO2 concentrations.

Do we really want to conduct an irreversible global science experiment to see who's right?