Imagine for a minute what it would take to make a world wide commitment to shut down 100% of all fossil fuel power within 30 years. A few small measures aren't going to do it, it will have to become priority one, and not just in the US or Europe, but worldwide.
European climate package of 2008 dictate that by 2020, 30% of all energy use must come from renewable sources.
Denmark's current climate policy target 100% renewable energi by 2050 (35 years from now).
Both goals are considered fully possible.
It isn't exactly a 100% global commitment, nor exactly 30 years, but it is doable, and there are people (and governments) with the will to do this - simply leaning back and saying, "it's hopeless" will get us nowhere.
Before you say, "ah, but DK is a small country", consider that several individual states in the US are smaller/denser, and could pursue the same goal since, you know, "America #1!!!".
9 US states are smaller by area (43k sqkm, Maryland = 32k sqm)
30 US states are smaller by population (5m6, Minnesota = 5m4)
42 US states have lower population density (333/sqmi, Pennsylvania = 286/sqmi)
Finally, if you need a different reason than "perhaps climate change is caused by humans", then I think we have several of these. Example: