Without objective evidence of positive or negative bias being stronger one way or the other, you should expect these biases to cancel each other out except for increased sensitivity. That is to say you will need to read more sources to get a clear picture than you would if everyone was being objective, but you should still expect the average source to be accurate adjusting for source quality. But I wouldn't worry about it. Take a look at the policymakers summary from IPCC; specifically page 19. They're estimating only weak impacts to the economy currently unless you live in a mostly coastal country.
IPCC AR5 summary |
