"Oh, I've seen fire and I've seen rain. . ." - James Taylor I just got back from a business trip to Spokane, Washington. There was so much smoke from regional forest fires that at times the sun was dark orange in color and the sky was an ugly brown-tinged gray I could only describe as apocalyptic. My sister in New Mexico has seen the same phenomenon this year. I have talked to many people who think it's arrogant to believe that humans are having any influence on the planet, let alone a profound one. The facts say otherwise. In any given year, humans move more dirt and rock than all the natural processes of erosion combined. Heck, human-caused changes to the Earth's surface are easily visible from space. Humans are a recognized agent of geologic change, so why is it so hard a stretch to believe we can be agents of atmospheric change? In my last column, I talked about the almost instantaneous increase in carbon dioxide (CO2) concentrations over the last two centuries (instantaneous from a geologic time perspective). Where did all this additional CO2 come from? Not from volcanoes. Volcanoes discharge at most, about 300 million tons of CO2 into the air per year but the increase in CO2 in our atmosphere is caused by the annual injection of 30 billion tons of CO2 (billion . . . with a B). A quick aside - volcanic eruptions can cause climate disruption - but the effect would be to cool the climate, not heat it up, and then only for a period of a few years. Ultimately, the carbon part of the CO2 comes from underground where it has been bound up as coal, oil, or natural gas. Most of the coal comes from deposits that are 300 to 360 million years old, from a time called, appropriately, the Carboniferous, when great swamps covered large parts of the world, dragonflies were as big as eagles, and the ancestors of salamanders were the size of alligators. Through our burning of fossil fuels, we are releasing in a matter of a couple of hundred years, carbon as CO2 that has not seen the light of day for a couple of hundred million years. There is simply no other source for all this CO2 that can explain the observations. CO2 is the most common, but not the most powerful, man-made greenhouse gas. Methane (natural gas) and the refrigerants we use in air conditioning are many times more efficient at absorbing heat energy. Even water vapor can be a powerful greenhouse gas; however, methane stays in the atmosphere for a decade or two, water cycles in and out of the air in a day or two, but the CO2 we put into the air today is going to stay there for the better part of a millennium. We are an agent of atmospheric change. In previous columns, I have talked about how the climate has been unstable. This instability is caused by "forcings," a term used by climate scientists to describe processes that cause climate shifts. Among the many forcings are changes in ocean circulation, ocean temperature, the amount of sunlight hitting the northern hemisphere in summer, the amount of tree cover, the area and volume of ice in the Arctic and Antarctic, the sulfur compounds spewed by volcanoes, and CO2. Shifts in any of these parameters will cause changes in others, leading to the feedback loops I discussed in this column previously. Over time, all these forcings equal out and the climate settles into a new period of equilibrium. We already know from geologic history that a new equilibrium could include Westborough being under 10,000 feet of ice for many thousands of years, or a mild temperate climate with four seasons and no extremes. Climate scientists are very certain that we are forcing the climate to shift. The question is, what is it shifting to? What will be the new equilibrium? Climate scientists have created massive computer models to simulate our atmosphere and its interactions with the land and oceans. These models do not predict the weather, they predict what the climate will be like in a given region over the next century. Dozens of models created over the decades by various researchers all say the same thing, adding CO2 to the air at the rates we are doing now warms the atmosphere causing shifts in the climate. These models predict that hot and dry regions will get hotter and drier. Regions that normally get rain will get more of it. The high, northern latitudes will warm faster than the temperate latitudes (like New England). So what do we see today? Look at the southwestern U.S. or Australia. They are getting hotter and drier. We are getting at least 15 percent more precipitation here in New England than we did 30 years ago. The Arctic ice pack is decreasing, forest fires are raging across Western North America. Europe and South Asia are in the midst of record-breaking summer heatwaves. So far, 2015 is the hottest year in the last 130 years, from a global perspective. Theories in science are not hazy speculations; they are detailed explanations of facts that describe and predict conditions in nature. Good theories make testable predictions. If these predictions that can be verified, then you know you have a good theory. So far, the predictions of climate scientists have been pretty accurate. Also, remember, the geologic record also backs up what we are seeing now. The next question is, if climate science is sound, why is it considered so controversial? I will cover that in my next column. Originally published in the Westborough News 08/28/2015.