The Basics of Global Warming

How Much Is Too Much?

Already, people have increased the amount of CO₂, the chief global warming pollutant, in the atmosphere to 31 percent above pre-industrial levels.

There is more CO₂ in the atmosphere now than at any time in the last 650,000 years. Studies of the Earth’s climate history show that even small changes in CO₂ levels generally have come with significant shifts in the global average temperature. Scientists expect that, in the absence of effective policies to reduce greenhouse gas pollution, the global average temperature will increase another 2.0 degrees Fahrenheit to 11.5 degrees Fahrenheit by 2100.

Even if the temperature change is at the small end of the predictions, the alterations to the climate are expected to be serious: more intense storms, more pronounced droughts, coastal areas more severely eroded by rising seas.

At the high end of the predictions, the world could face abrupt, catastrophic and irreversible consequences.