A Facebook post claims the greenhouse effect doesn’t exist, arguing it would only work if the atmosphere acted like a solid barrier to stop convection.
This is false. Climate experts told AAP FactCheck the effect didn’t get its name because it works like a real greenhouse, but because the result of greenhouse gases is the same – higher temperatures.
It is just one of numerous social media posts to claim the greenhouse effect is a hoax.
This post (archived here) echoes the claim by referring to the hypotheses of 18th-century French mathematician Joseph Fourier, who theorised that what was keeping the earth’s surface anomalously warm was the atmosphere acting like glass holding heat in a container.
The post states Fourier has been misunderstood, and his point was the atmosphere could only act like a greenhouse if it could form solid layers like glass panels, which is impossible.
“Fourier actually refutes the climate radiative greenhouse effect and he actually performed the experiments which prove that it doesn’t exist,” the post reads.
However, climate scientists say the greenhouse effect is not a hoax and the radiative effect of greenhouse gases does increase temperatures, not by acting like a real greenhouse and stopping convection, but by absorbing heat radiation (infrared) emitted by the earth and changing the radiation balance.
Ian Jamie, from Macquarie University’s School of Natural Sciences, told AAP FactCheck greenhouse gases cause warming because they intercept the earth’s outgoing heat.
“The earth gets energy from the sun … The earth absorbs this energy and then radiates it as what we feel as heat,” Dr Jamie said.
“Most of the energy goes directly through the atmosphere and out into space. But, greenhouse gases absorb some of this radiation directly and get more energetic, and faster. This is what we detect as heat.
“As we put more greenhouse gases into the atmosphere, more of that outgoing radiation is intercepted and so the average temperature of the earth goes up.”
Peter Rayner, from the University of Melbourne, said there was a lot of public confusion about greenhouse gases.
“Increases in greenhouse gas concentration do block some heat leaving the earth,” Professor Rayner told AAP FactCheck.
“Because the total amount of heat arriving at and leaving the earth must ultimately balance and the amount incoming hasn’t changed, the earth warms slightly to compensate for the blocking.
“Greenhouses don’t work like this, so this confusion of terms is common.”
Kim Reid, from Monash University’s School of Earth Atmosphere and Environment, said a more suitable name for greenhouse gases would be “‘molecules that interact with infrared’, but it doesn’t quite have the same ring to it”.
“If earth had no atmosphere, the global average temperature of the planet would be about -6°C,” she said.
Earth’s surface temperature is about 15C, with the discrepancy due to the greenhouse effect.
“Greenhouse gases are molecules that absorb infrared radiation (IR),” Ms Reid said.
Ms Reid said these gases scattered the IR back down to earth “like a blanket that keeps you warm on a cold winter’s night”.
She said while a garden greenhouse prevented heat transfer via convection, greenhouse gases prevented infrared radiation escaping to space.
“Adding more greenhouse gases to the atmosphere is like adding more blankets to your bed.”
Steven Sherwood, from UNSW Sydney’s Climate Change Research Centre, said “greenhouse effect” had always been a misnomer.
“The way the whole planet cools itself is not by convection but by its infrared glow, which sends energy back to space,” Professor Sherwood said.
“So-called ‘greenhouse gases’ like carbon dioxide dim this glow, thereby warming the planet.
“The fact that the ‘greenhouse effect’ is not a perfect name does not mean that there is anything wrong with the science – we have known for well over a century how both kinds of ‘greenhouses’ work, and that burning coal would cause global warming.”
AAP FactCheck previously debunked a similar claim from an Australian politician, who said greenhouse gases don’t trap heat because they cannot stop convection.
The Verdict
The claim the greenhouse effect is a hoax is false.
Scientists told AAP FactCheck the “greenhouse effect” does not work by stopping convection and therefore trapping in heat like a real greenhouse.
They say the radiative effect, where greenhouse gases block some infrared radiation emitted from earth from reaching space, is real and is warming the globe.
False — The claim is inaccurate.
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