Much of the expected temperature increase from global warming is offset by a phenomenon known as "Global Dimming". Basically, the exhaust particles spewed out by jet engines at 35,000 feet reflect just enough sunlight back out into space to cancel out most of the temperature rise that increased levels of carbon dioxide cause. This effect was theorized, but not proven until the days after September 11, 2001, when the complete lack of US air traffic caused a measurable increase in ground temperatures over the expected levels for those dates and for the dates immediately prior. Global temperature swings caused by the carbon cycle are a geologic fact. All we're doing with CO2 emissions is speeding up an otherwise natural process.