A certain David Weissman asked a question on twitter:
The first few answers (listed above) didn’t seem very helpful. Not to worry, David. I’m here for you.
First, it depends on who you’re talking to and about what. If you’re discussing policy and/or politics, whether it’s with Bernie Sanders or James Inhofe or your drunk uncle, there’s little difference in what people mean by the phrases “global warming” and “climate change.”
Scientifically, it’s a different matter. The overall subject is climate change: the climate is changing, the reason is us. But there’s a lot to climate. There’s temperature, and humidity, and precipitation, and windiness and storminess and cloudiness and barometric pressure … boy there’s a lot to climate. Temperature is an important part of it, but it’s only one among many.
When we study how human activity (mainly: greenhouse gases) affects climate, we find that temperature should be the first climate variable to respond noticeably. We knew this well before the temperature increase was observed. Now, it’s observed.
Scientifically, that’s one of the things that sets global warming apart from climate change. The latter is about how all aspects of climate are changing, the former is all about the temperature.
There’s yet another difference.
Temperature fluctuates all the time, just like any climate variable. Look at those temperature graphs, be they global like in news reports or local, whether it’s daily variations or monthly means or yearly averages, you’ll notice that temperature fluctuates. Here, for instance, is yearly average global temperature anomaly according to NASA, for the whole planet Earth, from 1880 through 2018:
Yes, it fluctuates from year to year. It looks like it’ll never stop fluctuating.
But … there’s something else going on, not just fluctuation. There’s this overall tendency for temperature to get higher as time goes on. It’s not universal, not every year is hotter than the one before, but over the long haul, that tendency is pretty clear. We might even call it a “trend.”
I might even estimate it mathematically, and come up with this (the thick red line):
That line is an estimate of the trend, and since it’s changing over time, we have temperature change. In fact it’s going up, and if we test it mathetmatically we find that it’s not just a false appearance, it doesn’t just “look like” it’s going up by lucky (or unlucky) accident, it’s a real trend and it’s really changing and it’s really going up. That’s the magic “warming” everybody’s talking about. Since it’s happening to the whole-world average, it’s the “global” everybody’s talking about.
So, David, there you have it. GLOBAL WARMING is an upward (not downward) trend (not fluctuation) in global (not local) temperature. Climate change is any meaningful (i.e. not just fluctuations) change of any climate/weather variable.
If you comprehend just that much, then you know a lot more than some people do. If you have further questions just ask.
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