You've hit on one of the main issues with Global Warming. How much of it is a man made issue and how much of it is due to natural causes? There are a few reports that suggest that the ice caps on Mars are slowly receding too, so it may be in part due to changing solar activity. I see the next battle being exactly how much human activities are to blame.
Having said that, the debate over Global Warming is distracting in how it steers the conversation away from all of the other problems man-made pollution are causing. CO2 emissions appear to be the main factor in ocean acidification. Particulate pollution is a main factor in changing evaporation rates, rainfall frequency and lung disease. Nitrogen oxides contribute to acid rain. Heavy metals and radioactive metals from coal have a number of adverse health effects. Improper fracking installations can contaminate ground water. Tailing ponds can leak and contaminate surface water.
All of this seems to have taken a back seat. To be honest, I wonder if energy companies are quietly happy about this. Global Warming has so many shades of gray that it is easy for energy interests to dismiss it and for people to believe them. Traditional pollution is a lot more black and white, making it hard to wave away as quack science. Changing the conversation is a fantastic way to stop talking about it.
Because if we were talking about how 40-year old coal and oil fired power plants skirt modern pollution controls by doing upgrades under the guise of "repairs", allowing them to keep their grandfathered pollution limits, I think people would be really pissed. What's the point of companies like GE and Hitachi advertising their modern cleaner power plants during the nightly news when nobody is forced to buy them? If that was the center of topic, there would be a better chance of it changing.