by Alan Journet, SOCAN Co-facilitator April, 2020 (Updated November 2025)

The following represents an effort to summarize the consensus emerging from climate science that identifies our current understanding of that science in 12 points.

1. Much of the incoming radiation from the sun (particularly short-wave radiation) passes through the atmosphere to reach the Earth’s surface. Upon reaching the earth’s surface, this radiation transforms into longer wave infra-red radiation (heat) which radiates outwards.  Some of this outwardly radiating heat energy is trapped by gases in the atmosphere thus causing warming that, absent these gases, otherwise would not occur.
2. The properties of atmospheric gases in terms of retaining outwardly radiating heat was initially described nearly 200 years ago and has been elucidated and confirmed since.
3. Without these gases, the earth’s atmospheric temperature would average about 0°F or -18°C and the planet would be largely uninhabitable for humans.
4. The atmospheric gases responsible for retaining this outwardly radiating heat are primarily the naturally occurring gases carbon dioxide, methane, water vapor, and nitrous oxide augmented by man-made gases with a fluorocarbon base (chlorofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons and sulfur hexafluoride, for example).
5. When the Global Warming Potential (GWP – also designated the carbon dioxide equivalent CO₂e) of carbon dioxide is designated as 1, the other gases have a greater capacity to absorb heat energy, when compared to an equal weight of carbon dioxide. Because it is short-lived in the atmosphere, methane is assigned a 20-year GWP of about 80 in addition to the more standard 100-year GWP, which is about 30.  Meanwhile, nitrous oxide has a 100-year GWP of some 300 while the chlorofluorocarbons are in the thousands.
6. While some of the outwardly radiating heat is retained on Earth and contributes to warming of the atmosphere, by far the majority (in fact, 93.4%) increases the heat energy content of the oceans while only 2.3% (1/40^th of that retained by oceans) warms the atmosphere. Indeed, if it were not for the capacity of the oceans to absorb vast amounts of this heat energy, the average global lower atmospheric temperature could be as much as 122°F – over 60°F warmer than 2019 global average of 59°F. Fortunately, because of its high specific heat, water does not warm as fast of air or metal (for example) when exposed to a heat source. Interestingly, the last decade comprised the ten hottest years on record.
7. Since the industrial revolution, when fossil fuels were introduced into industry to be burned to generate energy that drives machines, but also as a result of human-induced land transformation, greenhouse gas emissions have increased.  Prior to the industrial revolution the overall atmospheric carbon dioxide equivalent concentration of these gases was about 285 parts per million (ppm), the same as the carbon dioxide concentration since the other gases contributed only a trivial amount.  The atmospheric carbon dioxide equivalent has since risen to over 500 ppm (a rise of some 215 ppm).  Among the greenhouse gases, carbon dioxide contributes about 65% of the warming while the other gases contribute the remaining 35%. This explains why it is crucial that we reduce emissions of all greenhouse gases not just carbon dioxide.
8. From the beginning of the industrial revolution to now, the average global temperature has risen about between 1.5°C and about 2°C.
9. To test the credibility of climate models, they have been run over the history for which we have temperature data – meaning from the late 1800s. Climate models applied to the historical global warming trend produce a curve very similar to that actually experienced when human-induced greenhouse gas emissions are included, but produce a trend much lower than actually observed values when human emissions are excluded.  This test of the credibility of climate models suggests that they produce values closely resembling what we have historically seen, and are thus probably credible as projections for future conditions.
10. Although the models simulate historical temperature very closely, rather than producing projections that exaggerate the global warming trends and other consequences of warming, we find the actual historic trends fall either at the extreme high end of projections or the severity of actual patterns was slightly underestimated by the model projections.
11. Rather than following the projections of models that are based on assumptions that we limit the trend of increasing greenhouse gas emissions, actual warming has continued at the high end of the so-called ‘worst case scenario (Previously, the Representative Concentration Pathway or RCP 8.5; currently Shared Socioeconomic Pathway SSP 5-8.5) set of projections where it is assumed no efforts are undertaken to reduce emissions.
12. This pattern, if followed, would result in global warming of some 5°C (9.0°F) above the global 1850-1900 average by 2100 and if continued through 2300, warming of 8°C (14.4°F) or possibly as high as 12°C compared to that same average.

Implication:

Global warming of the dimensions projected on item 12 which assume we follow the RCP 8.5 / SSP5-8.5 trend, would induce climate changes sufficient to destroy natural ecosystems across the planet, and totally undermine our agriculture, forestry and fisheries long before 2300, possibly by 2100.

Those who do not accept the climate science consensus regarding global warming and its climate change consequences, have a huge body of science to challenge.  However, what is clear is that not everyone balks at the same conclusion emerging from climate sciences.  One approach when communicating with climate consensus skeptics is to identify where, in the above sequence, they break from the current climate consensus.

If anyone would like an expanded discussion of this twelve-point sequence, please contact me: Alan Journet.