If you want to focus reducing impact then for CO2 there are many sources for it in developing nations. The US EPA (quick, archive it before it goes away!) lists these for the US[1]; Electricity (35%), Transportation (32%), Industry (15%), Residential & Commercial (10%), and others at 7%. Any endeavor which is cutting into transportation or electricity generation specifically will be most impactful but there are places like better LED lighting for business (reduce commercial electricity consumption). Pretty well plowed but they can always use the help.

To act on reducing the existing gas levels perhaps the best place will be sequestration exercises. Generally it helps to have a Chemistry background here because many of the sequestration techniques consist of converting CO2 vapor into something that holds on to the Carbon. There are more mechanical solutions (pumping gas into mines) and there are biological solutions (growing plants rapidly and then burying them) as well. From a software perspective I would imagine the biggest use would be control systems software as these are essentially industrial processes that folks are trying to automate.

Finally if you're looking at living with it, then there things like modelling immersion maps for the coastal areas and helping cities plan to migrate to higher land. There are efforts to design more weather tolerant living structures to survive larger and more sustained weather events, and storage and recycling systems to maximize the use of local resources which may become scarce in a different climate.

[1] https://www.epa.gov/ghgemissions/overview-greenhouse-gases#c...