31 July 2014
Your filling the backyard pool for summer, and the kids are asking how long it will take to fill up. Now, you could just use simple math (using the gallons per minute you are adding to the pool divided by the total volume) and get an answer, but lets say you forgot to ask what it was and the internet is down, so you can’t look it up. Well, you could go out and measure how fast the water level is rising, but you suspect you might have a leak, and it’s also a windy day. Still, it’s your best bet, so out you go and you take a measurement followed by another twenty minutes later. Let’s assume the second measurement shows NO RISE in water level. Do you have a leak? Maybe, but the wind was making waves in the water, and the dog had just jumped into the pool as you were taking the measurement, so the water could be sloshing a few inches and you are uncertain. Trust me, you have every right to be!
Measuring the Earth’s temperature is in many ways very similar to the problem our back yard Dad is facing. The increasing greenhouse gases are trapping more and more heat, and we can actually do the math and come up with a very close estimate of how much. The problem is that there are natural oscillations in the atmosphere and oceans that affect the global temperature, so looking at the temperature from month to month or even year to year is going to show you the combination of all of these mixed in along with the rise from greenhouse warming. This is why you should always turn on alarm bells when you see a graph of the Earth’s temperature over a period of a few years, or even a couple of decades, because It’s showing you a mix of natural and anthropogenic oscillations.
I still see these graphs frequently on false science websites claiming climate change is a hoax, or that “global warming has stopped” etc. It’s actually very possible for the surface temperature to hold steady or even drop, as the earth’s outgoing radiation drops compared to what is coming in. Climate simulations have shown that even as temps rise over a century by several degrees celsius, there are period of steady and even declining temperatures over periods of up to a decade.
So, is there a better way? According to researchers at the UK Met Office, the answer is yes. The oceans hold most of the planets warmth, not the atmosphere and using data from the latest most sophisticated CMIP 5 project models, they have shown that an accurate measure of the ocean heat content will give you a better measure of the total Earth temperature. They have published a paper in the journal Environmental Research Letters and they made a video describing what they did and what they found here: