New Scientist has a long, yet provocative article pointing out that alternative energies may be subject to the law of unintended consequences. That is, at present, renewable energy sources such as wind and solar have very little effect on the earth’s climate—but only because they make up such an infinitesimal portion of our energy compared to fossil fuels. But if these alternatives accounted for a larger percentage of our energy sourcing, their contribution to climate change would increase as well (localized effects of wind farms on climate, for example, have been quantified). After all: “Whatever you use energy for, it almost all ends up as waste heat.” At present, humankind uses 16 terawatts (TW) of power at any given moment, substantially less than the 120,000 TW of power the Earth absorbs from the Sun. However, as humanity expands and uses more power, the contribution of heat to the Earth’s energy budget will increase. Eric Chaisson, of the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass., has calculated that if our demand for power increased to 5000 TW, it would warm the planet by 3 C°. Does 5000 TW seem unreasonably large? Perhaps. But: “[I]f our consumption continues to grow exponentially—it has been increasing by around 2 per cent per year this century despite rising prices—we could reach this point around 2300.” By the way, this waste-heat warming calculation doesn’t include the effects of magnifiers such as CO2 or other GHGs. Does this mean we need to restrict our energy use? Not necessarily:
If you turn the sun’s energy into electricity and use it to boil your kettle, it won’t make the planet any warmer than if that same energy had instead gone into heating up the tiles on your roof. But if you boil your kettle using energy from fossil fuels or a nuclear power plant, you are adding extra heat. “The only energy that is not going to additionally heat the Earth is solar and its derivatives,” says Chaisson, referring to sources driven by the sun’s heat—wind, hydro and waves.
Should we worry about waste-heat increases, even as there is still a long road ahead in curbing GHG emissions? Experts believe it would be prudent to worry about both simultaneously. “[I]f we do not start thinking about it now, we may one day discover that in trying to solve one climate problem, we have created another.”