The thing about Walter's graph is that it shows the last 25 years during which there has been a huge improvement in fuel efficiency, enormous reductions in factory emissions, waste clean up, tremendous improvements in home air conditioning and heating systems, and much heightened awareness of ecology, climate, and environment. The warming rate is shown as huge.
In the previous 25 years during which 12 mpg was considered normal and 15 mpg was good on our cars, nobody ever heard of a catalytic converter, smokestakes still belched megatons of pollutants into the air, we used freon in our refrigeration systems, etc., the warming rate was much lower and/or actually went down.
If we use data like that as significant, it seems all this environmental consciousness is what is causing global warming.