6 December 2015
The Climate’s Always Changing
This has to be the climate denier myth of the year, and it’s especially popular among politicians. I know of more than one climate expert, who upon hearing it from someone, likes to say:
“Really?? I had no idea!! All those courses, all that math! All that physics! No one ever said a thing about that! I should get my tuition back!”
The most effective propaganda, is a simple truth that leads someone to believe a lie. The “climate is always changing” is a classic case, and if you’re a sloppy thinker it can let you protect the bubble around your worldview. No wonder it’s a favorite of some politicians! Yes, “the climate is always changing”, but that doesn’t imply that we aren’t dangerously tampering with it. So, with that said, let’s wander in the world of facts and evidence for a while, and see if we can use one truth to lead us to several.
Some Basic Undeniable Facts
FACT ONE: Yes, the climate has been dramatically different in the past, and we know why too. The changes are caused by changes in the Earth’s orbit around the sun. These Milankovitch cycles happen very, very, slowly. Far too slowly to be noticed in even a few consecutive human lifetimes.
FACT TWO: Nothing in what you read above negates the fact that greenhouse gases (like CO2, and Methane) trap heat, and warm the planet. If we had no CO2, the Earth would be about 33 degrees C colder than now, and the oceans would freeze! It’s a MYTH that we are at the perfect distance from the sun. We are actually too far away, but CO2 has saved us, and kept our planet habitable. That fact alone proves that CO2 is an important greenhouse gas, and is a main driver of the Earth’s climate.
FACT THREE: The amount of heat being trapped by CO2 is known rather precisely (see the graphic above), and the physics has been understood for 150 years. Precise calculations were first done about a century ago, and have been refined more since. In 2011 the CO2 alone was trapping about 1.68 watts per square meter of heat. Air pollution was fortunately reflecting some of this, but the overall human effect on our climate is now between 1.1 and 3.3 watts per sq. meter, over every square meter of Earth. If we double the co2 level, then by the end of the century we’ll be trapping about 5 watts per sq. meter. Remember the old-time christmas tree bulbs, the kind that get to hot to touch? That’s about 5 watts of heat. Now imagine one of these over every square meter of the planet. (We’ve already added one over every-other meter, and the air is warming.)
FACT FOUR: The rising greenhouse gas levels are causing the climate to change at a rate of over 100 times faster than it did when it was only the orbital variations causing it. Yes, the planet’s temperature oscillates in a narrow range, and over millennia it can change dramatically, but the rising temperatures of the past 75 years are mostly the result of human activity. Incredibly,13 of the last 15 years have been the hottest on the instrument record. The odds of this happening as part of a natural oscillation are about 1 in 27 million!! Look at the graphic below of the planet’s temperature for the past 2000 years, you can see the magnitude of the natural climate oscillation, and at the end, the rapid rise due to carbon.
Now look at the image below, and you can see the Milankovitch cycle warming us out of the ice age 10,000 years ago, and the peak warmth of the holocene around 6,000 years ago, followed by the slow slide back down, until the greenhouse gases overwhelm the orbital cycle. Rather scary isn’t it!
So, the short of it is this: The silly claims by politicians that the temperature record (by 4 separate groups in 3 different nations) is not trustworthy, or that climate change stopped in 1999 (and all the other crackpot ideas) don’t amount to a hill of beans. If you want to prove that we have nothing to worry about, then you need to prove that greenhouse gases don’t trap heat. Good luck with that because you’ll have to overturn a century of physics.
Dr. Scott Denning at Colorado State has developed an excellent slide show for the public that explains this (We met last fall at a short course on climate at the NWA in OKC). His talk was beyond excellent, and he sent those of us who presented his slides (Go Here). You can watch a talk by Scott here.
From now on, when you hear “The climate is always changing!” your response should be “Yes, and carbon warms the planet. Period.”. The physics doesn’t lie, and that’s the real truth. The only two reasons for not accepting this is not understanding the science, or not wanting to, due to political worldview. I can help with the former, but not the latter.
Note: I wrote this for the many folks who hear this “climate is always changing” claim on cable news and from politicians. Don’t waste your time sending it to your uncle who thinks the chemtrails are real, and climate change is a commie plot, because it won’t work. When your are beyond accepting evidence based fact, there’s little that can be done. It’s just for those of you who have wondered what the real science looks like.