A new scientific paper just accepted for publication by the American Geophysical Union (AGU) shows that, on the basis of both computations and experimental measurements, the net rate at which Planet Earth is absorbing solar energy has increased between years 2005 and 2019. Planet Earth is heating up — global warming — at a faster rate, and that rate is increasing.
In my article here, I will first quote the abstract of this paper (“Satellite and Ocean Data Reveal Marked Increase in Earth’s Heating Rate,” by Norman G. Loeb, Gregory C. Johnson, Tyler J. Thorsen, John M. Lyman, Fred G. Rose, Seiji Kato, 15 June 2021;, and then give my interpretation of the overall scientific conclusion, in plain English.
Abstract from the AGU paper.
Earth’s Energy Imbalance (EEI) is a relatively small (presently ∼0.3%) difference between global mean solar radiation absorbed and thermal infrared radiation emitted to space. EEI is set by natural and anthropogenic climate forcings and the climate system’s response to those forcings. It is also influenced by internal variations within the climate system. Most of EEI warms the ocean; the remainder heats the land, melts ice, and warms the atmosphere. We show that independent satellite and in situ observations each yield statistically indistinguishable decadal increases in EEI from mid-2005 to mid-2019 of 0.50±0.47 W m-2 decade-1 (5%-95% confidence interval). This trend is primarily due to an increase in absorbed solar radiation associated with decreased reflection by clouds and sea-ice and a decrease in outgoing longwave radiation (OLR) due to increases in trace gases and water vapor. These changes combined exceed a positive trend in OLR due to increasing global mean temperatures.
Earth’s increased temperature has melted ice and snow and reduced cloud cover, which means that less solar radiation (light) is reflected back into space — a warming effect. Note that clouds, snow and ice fields are white and highly reflective of light; bare ground and the ocean surface have much lower reflectivity. Planet Earth’s net reflectivity is called the albedo; and it has decreased.
Even though the increased average global temperature has warmed — stored heat in — the oceans (a 91% effect, as only 9% warms the lands and air) and thus caused greater evaporation of water (and snow melt and ice melt) into the atmosphere, fewer clouds are forming because the higher air temperature keeps the water vapor from condensing as quickly as in previously cooler times. Note that clouds are cold, they are made up of water droplets and ice crystals: condensate from cooled vapor.
However, the ever increasing atmospheric load of carbon dioxide (CO2) and other greenhouse gases that humans cause to be emitted, along with the increased water vapor in the atmosphere, just noted, make for a denser gaseous “filter” or capture medium for the outgoing Infrared Radiation (Outgoing Long-wavelength Radiation = OLR = HEAT) that cools the Earth.
For Planet Earth to be in thermal equilibrium — at a steady average global temperature — the rate of heat-energy radiated out into space (cooling) must equal the rate of light-energy absorbed from the Sun (heating).
The quantity of thermal-energy emission per unit time (OLR) from any isolated body (like Planet Earth suspended in space) increases as its temperature increases. This phenomenon is known as the “blackbody radiation” effect in physics, and quantified by the Stephan-Boltzmann Law. So, one might have hoped that with Planet Earth’s now higher average temperature that it would reject heat (and cool) at a higher rate; and in that way seek to maintain a steady planetary temperature.
BUT the AGU paper shows that the decrease of Earth’s light reflectivity (albedo), combined with the increase of its OLR (heat) absorptivity by the atmosphere, overwhelm the also increased rate of heat (IR or OLR) emission from the planetary surface back towards space.
The net effect is an increase in the rate at which originally-solar energy is absorbed by Planet Earth, and hence an increase in the rate at which Planet Earth’s average temperature is increasing. This is a self-reinforcing effect, a.k.a.: a vicious cycle.
Immediately ceasing “all” (the vast majority of) emissions of carbon-dioxide and greenhouse gases is the first essential step to SLOWING the rate of global warming and attendant “climate change”, and the absolute beginning of a very long process of global temperature equilibration:
1/ from a slowing of the rising trend of temperature;
2/ until temperature reaches a plateau; because it takes decades to centuries for the oceans and lands to reach a temperature equilibrium — think of equilibrium as “uniformity,” though that analogy is not exact;
3/ and then the slow (decades to centuries) re-absorption of CO2 from the atmosphere by the surface waters of the oceans and photosynthesis (plants);
4/ with a gradual (centuries to millennia) reduction of global temperature.
It took 200,000 years to clear away the global warming “hyperthermal” event known as the Paleocene-Eocene Thermal Maximum (PETM), which occurred ~55.5 million years ago.
The sooner the emissions of greenhouse gases cease: the lower the height of the inevitable maximum temperature plateau, and the shorter the duration of the period before temperature returns to “normal” (as in the Holocene). Regardless, that duration will be vastly longer than a human lifetime, and even many human generations.
The social and political implications of these scientific findings quickly become obvious on honest reflection.
[Thanks to Peter Carter for the AGU reference.]