Perhaps you've heard a friend say, "Okay, I believe climate change is happening, but I'm not a scientist, and don't really understand the science behind it." Well, you don't have to be a scientist to understand it. Look at boiling water. Seriously. What happens when you boil water? You're adding heat to a pot of fluid. The fluid starts moving around as it heats up, eventually evaporating so fast that big boiling bubbles are produced.
Think of Earth as a big ball, covered with a fluid mix of water and air. The sun heats water and air, and some heat becomes motion, moving the air and water around the ball, just like heating moves water in a pot. The long-term patterns of this heating and movements are our climate, changing slowly enough over eons so that most life can adapt to it. But add to this water-air mixture a sudden jolt of heat, and the planetary water cycle suddenly speeds up and changes. This results in bigger and stronger storms and floods. The extra heat creates more extreme heat waves, droughts, and melts ice globally, which raises sea levels. All this is threatening our sources of food, water and shelter, the basics of our survival. Was that a bit fast?
Alright, let's just dissect this a little. How does Earth trap the Sun's heat? Certain gases, like carbon dioxide and water vapor, comprise less than one percent of our atmosphere, but trap direct or reflected sunlight and convert it into heat, releasing it for absorption by air, water and land. The gases can also recapture and release the heat repeatedly. The levels of these so-called greenhouse gases have basically acted like a balanced solar cooker, converting just enough light into heat to create good climatic conditions for our evolution and survival. Until recently, that is.
Burning fossil fuels such as coal, oil and gas for our energy is increasing levels of greenhouse gases, especially carbon dioxide, in the atmosphere, unbalancing our global solar cooker. So, our planet has warmed over one degree Fahrenheit, and will continue to heat further and faster, as more greenhouse gases build up from more burning and feedback effects. Feedbacks? A nasty side-effect of the initial heating from carbon dioxide is that more water evaporates, creating more water vapor, a potent greenhouse gas. Heating is also melting ice globally, turning white, sun-reflecting areas into dark, sunlight-absorbing ones that convert the light to heat. Also, as soil heats, it releases more greenhouse gases, including the very potent greenhouse gas methane (aka natural gas), especially from the Arctic, where global heating is occurring much faster than elsewhere. So heating begets... well, more heating. In fact, most of the heating comes from the feedback effects, not the initial conversion of sunlight to heat.
Viewed from the recent geologic timescale chronicling Earth's climate, humans have added a planetary jolt of heat, souping up the solar cooker. The heat doesn't sound like much, but a little goes a long way towards changing climate. And, actually, the heat isn't that little. Although the total average increase in temperature is small so far, this constant infusion of extra heat is "a lot of energy," says senior climate scientist Warren Washington at the National Center on Atmospheric Research. Just how much? 250-500 million Megawatts of energy. That's the amount of heat that would be produced if we had up to a half million more large power plants on Earth, operating full-time, year after year.
Scientists predict that our planet could heat up another 6 to 11 degrees by the end of this century, roughly the same difference in temperature that separates our climate from the last ice age, when 300-foot thick ice sheets covered the northern U.S. So, our planetary pot of fluids doesn't have to even approach boiling (and probably wouldn't) to dramatically affect our survival.
We're heating our planetary pot of fluids fast, as the animated NASA global map shows. Some of that heat converts to moving energy, which moves fluids, both air and water, around faster. The planetary water cycle is speeding up: more water goes up (evaporation), comes down (rain, especially) and runs off, yearly. In general, the wet gets wetter, the dry, drier -- think droughts and floods, like Texas is experiencing. This more extreme shifting of energy also results in cold getting colder, warm getting warmer (heat waves). Air is also moving faster. This means more energetic storms, from cyclones to hurricanes, and winds speeding up, such as the Antarctic westerlies. And shifting wind patterns: our tropical belts are widening, moving their jet-streams poleward, pushing the dry subtropical climate zone further into the southern U.S. -- read more droughts.
Just like one can't predict the next bubble rising in boiling water, so, too, the planetary scale of climate complexity prevents making detailed, local, climate predictions. But, in general, the outlook is not good. All of the above results in more extreme weather, which will get more extreme as the unbalanced heating continues.
The good news is that we can stop too much harmful climate change if we act fast, and stop emitting global warming gases, mostly by: a) using energy more efficiently; b) switching from fossil fuels to clean renewable energy (solar, wind, geothermal), and c) stopping deforestation. Technically, we can do this. Doing so would create more jobs and improve our economy, as other countries have shown. Bringing our world population down to sustainable levels would also help enormously.
Changing energy sources won't be easy politically, or cheap. But it's cheaper than what we're doing now. We've spent trillions defending foreign oil sources. Fossil fuel pollution and mining inflict heavy costs on human health and our environment. So, even if climate change wasn't happening, it pays for us to switch to renewables and efficiency anyway.
Meanwhile, next time someone tells you they don't understand climate change, tell them to go boil water.