Although the UN Intergovernmental Panel on Climate Change (IPCC), the foremost authority on climate science, has been startlingly accurate in its forecasts about climate change over the years, the group is being criticized for being too conservative.
The IPCC's first report, issued back in 1990, successfully predicted what we're experiencing today, according to research by Dáithí Stone at Lawrence Berkeley National Lab. Thousands of scientists contribute to the reports, and their predictions and observed increases in temperatures all match up. It's even more impressive considering that scientists used much simpler computer models 22 years ago.
That's because "The prediction basically depended on how much carbon dioxide was already in the atmosphere, and that has been what's important," says Stone.
But because the IPCC has an inherently conservative bias (as scientists do), they have consistently underestimated the rate and intensity of climate change – which means we haven't been planning adequately for its impact. Countries may have been dragging their feet at least partially because they didn't understand the true, immediate effects.
Governments and the public could be blindsided by the rapid onset of the flooding, extreme storms, drought, and other impacts associated with catastrophic global warming, says an analysis by The Daily Climate.
For example, in its 2007 report, IPCC estimated the Arctic would be ice-free during the summer in 2070, but now we know that could happen within 20 years. The Arctic is melting 50% faster than IPCC projected.
The same is true for rising sea levels. IPCC's 2001 report forecast annual rises in sea-level under 2 millimeters, but oceans have risen more than 50% more - 3.3 millimeters per year, and are rising particularly quickly on the US coasts.
US Faces Warmest Year on Record
The last 11 months in the US are already the warmest on record – with a national average temperature of 57.1 degrees F, 3.3 degrees above average, according to the National Oceanic and Atmospheric Administration (NOAA).
It is virtually certain that 2012 will surpass 2008 as the warmest year on record for the nation.
The world is already dangerously close to the 2 degrees Celsius rise that world leaders have pledged to avoid. A recent UN report suggests emissions are now 14% higher than they need to be to hold temperatures below the 2C rise - with devastating implications for coastal flooding, food and water shortages, and droughts.
Read the analysis: