When people talk about "temperature" they mean air temperature, look at any weather forecast. Human survival is largely dependent on air temperature. While water does evaporate faster at 150 than at, say, 100, it is still well below boiling and not hard to contain -- 150 is a somewhat cooled cup of tea/coffee. Underground piping will be much colder than ground temperature.

At any rate, temperature increase forecasts for the next 100 years are all in the O(1 degree C) range. There are many reasons to mitigate climate change/decrease green house gas output/fight pollution, but let's not spread FUD.