The essential concepts
- The principal gases in the Earth’s atmosphere - nitrogen, oxygen and argon which together comprise over 99% of the earth’s atmosphere - neither absorb nor emit radiation.
- Carbon dioxide is a greenhouse or radiatively active gas, endowed with the propensity to absorb heat, as does water vapour in its gaseous form. Only gases which can absorb longwave (infrared), low photon energy radiation can reradiate the Earth’s energy. This interaction between photons and CO2 molecules is Einstein physics at its most basic.
- Endowed with this resultant concentration of excess energy, the Earth’s surface and lower atmosphere have warmed up resulting in increased trapped heat, and causing a rise in the earth’s surface temperature.
- The actual proportion of carbon dioxide in the atmosphere is actually quite small, almost minuscule one might say: only 0.04% or 400 parts per million (ppm), but it accumulates to form a blanket, thereby causing the earth's temperatures to rise.
- This level has increased from 280 ppm in pre-industrial times, a rise in the order of 43%, attributed largely to fossil fuel burning. As at 11 May 2019, it was 415.26 ppm, the highest it has ever been. On 16 July 2020, at 415.20 ppm, the figure stood virtually unchanged since the year before. They have since moderated somewhat following Covid-19 restrictions resulting in lesser aviation emissions. For the most recent figures, see https://scripps.ucsd.edu/programs/keelingcurve
- In 2016 carbon dioxide levels rose globally by a record rate of more than 3 ppm raising temperatures from pre-industrial levels to beyond 1.5 degrees and 1.35 degrees above the norm for the 1951-1980 period.
- This is known as the enhanced greenhouse effect or, to use the common parlance, “climate change”.
- These effects have been felt more strongly in the Arctic than elsewhere on the planet.
- Although the rest of the world has observed a modest temperature increase of about 0.8 degrees Celsius since the beginning of the 20th century, average temperatures in the Arctic have warmed by more than double that over the past 50 years, and 2 to 3 times faster than the rest of the Northern Hemisphere, a phenomenon known as Arctic amplification.
- This has resulted in the rapid loss of summer sea ice in the Arctic, diminishing its albedo (the propensity to reflect light and heat back into the atmosphere).
- Some 93% of this excess energy has been absorbed by the oceans.
- The loss of sea ice and ocean warming have also led to a weakened polar vortex, with the result that the polar winds which usually flow west to east in a circular loop and stay confined to the Arctic have now spilled south leading to a weakening of the jet stream, resulting in large amplitude loops which have tended to become stuck in place leading to a succession of long-lasting extreme weather events in the nature of hurricanes, heat waves, wildfires and drought in different parts of the northern hemisphere.
- The object of the Paris accord is to limit global temperature increases to 1.5 to 2 degrees above pre-industrial times, but even if this is fully achieved, it may not be sufficient. At present, we are nowhere near on track to meet the Paris Agreement target.
- Half of the carbon now in the atmosphere was put there in the last 30 years, and even under current pledges to cut emissions, the world is on track for a nightmare three degrees of warming or more by the end of this century. Greenhouse gas concentrations in the atmosphere - the main driver for climate change - reached the highest levels in at least 3 million years in 2018.
- Carbon dioxide, which makes up about 80 per cent of the heat-trapping potential of these gases, is now almost 50 per cent more abundant in the atmosphere than in 1750.
- And even should we achieve that magical 1.5 degrees above pre-industrial times, which is highly unlikely, we will still not have solved the problem, only what causes it. All the existing carbon will still be remaining in the atmosphere, necessitating all sorts of projected bizarre solutions gathered generally under the rubric of geoengineering to remove it.
- The risk is not so much of runaway global warming but rather of a world stabilising at perhaps 5 degrees warmer, which will make it a much tougher climate for our children and grandchildren to live in.
In aid of the foregoing, one need only consult Sir David Attenborough’s 2019 BBC documentary Climate Change: The Facts, where Sir David adds the weight of his considerable reputation and expertise comprising more than half a century of hands-on experience in this area to the testimony of a plethora of climate change scientists from across the globe and across the spectrum.