To the editor:
In his March 16 letter, Ross Wilkinson says that changes in the intensity of sunlight are “primarily to blame for short-term changes in Earth’s surface temperatures and not ‘greenhouse gases.’”
I agree that changes in solar intensity are primarily responsible for initiating transitions from warm inter-glacial periods to ice ages and back again.
However, climate scientists have shown that alterations in solar radiation are insufficient by themselves to drive the climate from an interglacial to an ice age, or from an ice age to an interglacial. The major portion of each temperature transition is fueled by changes in the levels of greenhouse gases in Earth’s atmosphere, by mechanisms I’ve described in two previous letters (Feb. 21 and March 8).
Our current warming is different. It’s been so rapid that septuagenarians like me can easily feel it. While growing up in New Jersey, I could ice skate on local ponds for much of the winter. Now I have difficulty finding good skating even here in New Hampshire. This warming cannot be explained by the sun, because solar intensity has decreased during these years. But it can be explained by greenhouse gases such as carbon dioxide, which has increased in our atmosphere by 40 percent since the 19th century, due to our burning fossil fuels.
What especially frightens me is the fact that the rate at which Earth’s temperature is currently increasing is similar to what happened during the great extinctions studied by paleontologists, times when massive volcanic activity spewed huge amounts of carbon dioxide into our atmosphere, so the climate warmed rapidly, and most life went extinct. If we wish to avoid a similar fate, we need to find ways to smoothly, but rapidly, replace fossil fuels with clean energy. Citizens’ Climate Lobby offers a plan.
Joel A. Huberman
Peterborough