Claim: "CO2
Follows Temperature, Not the Other Way Around"
Why this Claim is Deliberately Misleading: Look at the logic this claim attempts to use to persuade you. Because
during the Ice Ages the paleoclimate record shows temperatures rising from
low levels, followed decades or perhaps a century or two later with rising CO2 levels, that therefore current CO2 rise cannot be causing global warming today. If your response
is puzzlement and a struggle to grasp the logic, be reassured - there is no logic to grasp.
Human forcings of climate have no precedent in the Ice Age paleo record. Before mankind was pumping huge amounts of carbon into
the atmosphere in a geological instant, the large slow temperature changes
of the past few million years were primarily caused by the Milankovitch cycles in the Earth's orbit. When temperature
rises due to orbital change, the rising ocean temperature brings more dissolved ocean CO2
out into the atmosphere (Callion et al. 2003). The increased CO2 in the atmosphere then
causes further temperature rise by the greenhouse effect, which induces more
CO2 out of the ocean, etc. This positive feedback, together with the ice albedo positive feedback effect, is sufficient to bring Earth
out of an Ice Age into an interglacial. It takes centuries for this process
to happen as the CO2 transfers into and out of the ocean are quite slow because global deep ocean currents are very slow, and because the process proceeds through stages of quasi-equilibrium. A
good discussion with figures is here,
and another is here.
The Callion et al. 2003 paper found a lag of ~800 years, but newer research which better understands the movement of air bubbles in paleo ice cores finds that lag was more like 200 years or less, with far smaller error bars (Parrenin et al. 2013 and digested in Scientific American here).
Today's global warming is happening not on the thousands of years time scales of the "CO2 Follows Temperature, Not the Other Way Around" canard, but a few decades. And the record clearly shows CO2 rise is happening at the same time as temperatures rise in the atmosphere and ocean - not ~200 years later. The reason is simple - we're adding CO2 directly to the atmosphere, at a pace far in excess of what the ocean or land can absorb. Not even remotely in equilibrium. It's not at all like the "CO2 follows temperature" example in the paleo record. Ten thousand years ago, coming out of the last great Ice Age, humans and their livestock comprised about 0.1% of the land vertebrate biomass. Today, we comprise almost 99%, and strongly altering the atmosphere as we dominate the planet.
We've understood the issue of Ice Age CO2 vs. Temperature leading/following for many decades, as publications in scientific journals have shown. A good 8 minute video with plenty of good visuals and citations of these papers over the years, is here. Climate denialists and the blog "Watts Up With That" by Fox News weatherman Anthony Watts, have done much harm in continuing to perpetuate this myth.
| In Short: It's deliberate red herring meant to confuse. It's wanting you to believe that the evidence in front of us - that rising CO2 is leading rising temperature today - must be wrong because that's not exactly what happened during past Ice Ages. There is NO logic to such a statement. They make this statement, leave it hanging, and expect you to take the bait. Today, our CO2 is causing warming directly to the atmosphere, heating it and the ground, lowering the ability for CO2 to be dissolved into the ocean and soil - and they are clearly happening at the same time. Coming out of Ice Ages, it was astronomically driven heating at the Arctic Circle which melted snow, darkening ground, raising surface temperatures, then raising ocean temperatures and causing dissolved CO2 to emerge into the atmosphere, further amplifying the now-CO2 driven heating in a positive feedback. In that case, one EXPECTS to see a lag in CO2 vs temperature, and that is what we see in the paleo record. |