One of the biggest but rarely told stories at the heart of anthropogenic climate change is the changing chemical make up of the seas as a result of increasing levels of CO2. For this reason, CO2 can be classed as a pollutant.
Increasing levels of atmospheric CO2, results in a proportion of that CO2 being absorbed by the water in our seas and oceans. This has both positive and negative impacts. The positive result of this absorbtion is that the amount of global warming is greatly reduced (whilst the seas and oceans can continue acting as a carbon sink). The negative result is the acidification of the seas and oceans.

This change to our seas and oceans is causing problems for a lot of life below the waves. In particular, creatures that create shells have serious problems. But also many fish depend on water with a specific range of ph level and temperature, if these change, then they can be forced to migrate or risk becoming extinct. A small number of species may benefit from the changes, such as some species of  'star fish'.

The Telegraph
Environment News Service
Environmental Research Web

New research published in Nature this week shows that time is running out if we are to limit global temperature rises to below 2^oc. Scientists are saying we need to put the brakes on the carbon emission producing society within a few decades. When we reach a trillion tonnes of anthropogenic CO₂, it is likely that global temperatures would exceed the 2^oc average increase that earths governments are trying to limit to.
In order to prevent temperatures exceeding the 2 degree limit, fossil fuel consumption world wide would need to be cut to a third of the total that could be recovered.

Nature (editorial)
RealClimate (Hit the brakes hard)
Greenhouse-gas emission targets for limiting global warming to 2 °C (Malte Meinshausen et al)
Warming caused by cumulative carbon emissions towards the trillionth tonne (Myles R. Allen et al)