Our worst case climate change scenarios are quite possibly much better than the reality will be.

From a discussion of hurricanes in The Weather Makers:

Some commentators believe that the discrepancy between the computer models and conditions in the real world somehow indicates that global warming is not responsible for the increasing cyclone activity. Others, however, believe it suggests what they have long suspected: that the global circulation models used to simulate future changes in climate are deeply conservative. [emphasis mine]

Trees rings are are often used to reconstruct climate. A recent paper about the affect of bugs eating those trees on the climate reconstructions had a similarly worrying conclusion:

Here, we have shown that herbivory by insects can result in the overestimation of the amplitude of variation. If overestimation has been a problem in past reconstructions, recent periods of extreme wet and dry may be further outside of the bounds of normal variation than previously realized, making current estimates of the magnitude of climate change overly conservative.

Now go buy some energy efficient light bulbs.