Does anyone know projects or other things I can have an impact on?
You will probably never write a magic thousand lines of code for this. You'll probably have a far greater impact if you do a few simple things we should all be doing anyway:
* Turn off lights you aren't using.
* Turn your air conditioning up or down by a few degrees.
* Turn your water heater down a few degrees.
For computer-specific stuff:
* Don't leave computers running when not in use.
* Dim your displays.
* Use your laptop's battery rather than leaving it plugged in all the time.
I know it's not exactly interesting stuff, and it certainly doesn't build your CV, but neither of those things is actually important when it comes to climate change.
It's easy and you can start right away. You are reducing your carbon footprint by probably 10 times the amount, of all the other suggestions you listed combined.
The only thing that is going to do anything about climate collapse (climate change is too wishy-washy for such a serious topic) is leaving the carbon in the ground or pulling it out of the air.
If I turn my water heater down I'll need to turn the hot tap on more when I have a shower, thereby using more not-so-heated water, resulting about the same amount of energy used.
Use your laptop's battery rather than leaving it plugged in all the time.
This one also doesn't work, because charging and discharging a battery results in energy lost as heat. Rechargeable batteries aren't 100% efficient.
And dimming your displays? I wouldn't worry about that, the handful of watt-hours I'd save a year doing that is grossly undone by forgetting something at the supermarket and driving back to get it.
Cycle or walk more, catch the bus / train / tram once a week, and as others have pointed out reduce consumption of animal products.
I reckon the only way to have any substantial impact is to influence others to change their behaviour / help drive political and economic change.
* our global economy needs further regulation to bake the cost of externalities (CO2 pollution) into the economy. Without a carbon tax or similar mechanism we get what we have today: polluting activities (on both supply / demand side) are effectively subsidised, so there is no incentive not to do them. We need to lobby for this.
* some in the climate movement talk about the "climate emergency" and want to phrase the response as some kind of world-war era national economic mobilisation. I think this makes sense, but this will only happen politically if a majority of the population think there is an emergency.
* someone else in the thread has already mentioned Jevons paradox - where improving the resource efficiency of a process in a market can result in an increase in overall consumption of the resource. Separately from that I think demand reduction should be a clear win. What can you do to reduce demand for energy?
As a developer, you can educate and help people conserve energy. Heating and cooling are enormous culprits. Learn to be comfortable at 60-65 in the winter, and 75-80 in the summer. Transportation is a big culprit as well. Buy a bicycle and use it for everything under 10 miles. Of course green technologies are helpful, and I don't mean to discount them, but the reality is that our cultural attitudes towards consumption are just as much of the problem.
To visually see what I mean, check out this graphic from the book: http://www.withouthotair.com/c18/page_109.shtml The red bar on the left represents a typical Britain's consumption (which, mind you, is statistically less than the typical American's). The green bar on the right represents the pie-in-the-sky most insanely optimistic output of all the green technologies. Like, if they covered the entire country in solar panels and surrounded it with windmills and tidal power. It's basically a completely unreasonable estimate of the top-end of green energy production, and it doesn't even match the consumption bar.
[1] http://www.goodreads.com/book/show/4070074-sustainable-energ...
check out Bret Victor's essay "What can a technologist do about climate change?" if you haven't read it, it's very good:
http://worrydream.com/#!/ClimateChange
Discussion on HN:
If you want to reduce climate change, I think you should just follow FroshKiller's advice. You might also evangelize solutions to the public and politicians that provide decent compromises with reduced pollutants. You should also pay campaign contributions to politicians most likely to do that as this counts more than ten thousand opinions from voters. These will collectively probably achieve nothing given industrial nations overall don't care about climate change vs money, jobs, and disposable goods. You'll at least be doing your part.
You can also stop buying products from most damaging companies [2]
[1] http://www.un.org/climatechange/take-action/
[2] http://www.sciencemag.org/news/2016/08/just-90-companies-are...
Make it easier to model genetic engineering so we can produce crops with less use of the Haber-Bosch process.
Make public transit easier to use.
Make it easier for people to coordinate life without a car.
Make inexpensive FLIR cameras for people to find leaks in their home insulation. NOTE: if this becomes widespread, it will be legal for police to use those same devices to look into people's homes.