Topic: Global warming and its effect on living organisms.  

need to focus on one or two questions/hypotheses that you can test or evaluate.

For example, how could you test if global warming is thinning the biosphere? You need to include some specific response variables to global warming that can be measured. 

How about comparing measure(s) of primary productivity over time between a region that is warming and one that is not as much? 

How about something to test changes in plant or soil microbes associated with the melting of the permafrost as a consequence of global warming?

You need to be very specific with a research question you can test experimentally or comparatively where you develop your research proposal.