The past week or so, there’s been a lot of discussion on the blogs I read about whether or not we should use the term “global warming”. Simon Donner covered it, then Michael Tobis put in his two cents, and Peter Sinclair discussed it on live TV. It got me thinking.
The term “global warming” doesn’t cover the implications of a rising temperature, just the fact that the average global temperature is rising. “Climate change” covers everything.
However, the public is far more acquainted with the term “global warming”, so it makes sense to keep it in use so we are understood. However, this term has led to many misconceptions. To the public, it’s often interpreted as “everywhere-in-the-world-all-the-time warming”. So every time it’s cold in Europe, or it snows on the Atlantic Coast, there are comments of “where’s global warming” from the usual suspects, and even reasonable people start to doubt the phenomenon.
Because we’ll never be able to completely replace the term “global warming” with something more accurate, I think it would be best to slightly alter it, in a way that will reinforce the idea of averages rather than variability, even to people who don’t use it. I think we should call it “net global warming“.
Really, this is exactly what the folks at NASA, NCDC, or any of the other global temperature monitoring stations calculate. They add up all the regional anomalies from thousands of weather stations to find a net anomaly for the entire planet. This way, we don’t know precisely what the absolute global temperature is, but we know how much it has changed overall. Some places are warmer, some places are colder, but this single annual value shows us at a glance what the planet’s temperature is doing.
Even that value doesn’t consistently warm every year – we don’t set a new temperature record every year – because the global climate has enough internal variability to slightly change, from year to year, the percentage of the planet’s heat that is stored at the surface, which is what NASA et al measures. La Niña, which made 2008 cooler than previous years, doesn’t actually change the total heat energy stored on earth. It just sucks some of it out of the atmosphere and into the oceans.
Luckily, La Niña has a friend, El Niño, which does the opposite to net global surface temperatures, so they basically cancel each other out every five years or so. All these short-term cycles of variability – ENSO, sunspots – average out over the years, and as time goes on we stop seeing the noise and start to see the trend. Look at the red line in NASA’s graph, rather than the jagged black line, to see less noise and more trend.
If we can get the idea of “net global warming”, rather than “everywhere-in-the-world-all-the-time warming”, into the public consciousness, our collective understanding of this problem will shoot up. Plus, we’ll be less prone to misleading statements like “It’s cold today, so there is no global warming” or “Warming stopped in 1998“.