Leftist Academic Bias
While a majority of academic economists could be described as "left of center", leftist tendencies are probably less pronounced than in for example sociology and most other social scientists.
The fact that the leftist bias is greater in natural sciences than in social sciences have particular significance in the climate debate. In most natural sciences, theories have little or no political implications, meaning that there is little reason to believe that political preferences could distort results. However, with regard to climate science, the results have political implications, meaning there is a reason to believe that scientists could manipulate results for political reasons.
And "Climategate" does prove that some manipulation does exist. Just how widespread it is among other climate scientists is less certain, and it is unlikely that all deliberately distort results, but it would be naive to think that it is completely non-existent among those not specifically implicated by "Climategate".