Letter: Yes, Sen. Romney, there is something we can do about climate change

I appreciate Sen. Mitt Romney acknowledging that the earth is warming and asking, “Do humans contribute to it?” (Tribune, Feb. 21). Fortunately, the answer has been well established by decades of scientific inquiry.Is it a natural cycle? No, because the current temperatures have risen too fast compared past changes. Volcanoes? No, for the small amount of greenhouse gas they have emitted can’t account for the observed warming. The sun? No, because solar irradiance has declined s