Firstly, it is. Secondly, it's manifestly obvious that if* the predictions are true and the planet's climate is materially changed, then the economic damage -- due to lost land, loss of crops, further extreme weather damage, etc etc -- would be more or less off the scale.
Besides which, it depends on how you implement the change. A switch to a greener economy isn't necessarily a loss, is can be an investment too. In the skilled jobs you need to design, build, install, manage various renewable energy sources, for example. I am not going to claim to have done a full cost-benefit analysis, and I have little doubt that if we were to change at the rate needed then it would be a, potentially huge, short-term economic hit -- but, this time at least, it would have been worth it.
*or perhaps more accurately, when they come true.