CLIMATE WATCH - Climate Myths
A Climate Myth about CO2 and temperature
We often see claims that "temperature always increases first, followed by a rise in CO2". The "sceptic" blogs quote this a lot, and the main error here is "always".
This sequence ONLY happens at the end of glacial stages, at the very beginning of deglaciation. In other geological contexts, CO2 rises first. But this one situation has become a key part of many "sceptic" comments.
So what is going on? The initial warming as deglaciation starts is driven by astronomical cycles, Milankovitch Cycles:
https://www.youtube.com/watch?v=iA788usYNWA&t=193s
Another https://www.youtube.com/watch?v=6lbJrvtxWNE
(I don't often post videos in scientific comments, but to illustrate these cycles it's the obvious thing to do)
This initial warming causes the oceans to release CO2. Then the CO2 amplifies the warming.
So rising temperature initially causes CO2 rise .... AND THEN THE INCREASE IN CO2 causes far more warming. Overall, about 90% of the global warming occurs after the CO2 increase.
https://www.carbonbrief.org/explainer-how-the-rise-and.../
This paper is the one I post when addressing this issue:
https://www.nature.com/articles/nature10915
"Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation" - Shakun et al (Nature, 2012)
Note that the 2nd sentence in the abstract is often as far as some readers go - it sets the problem that this paper addresses and resolves, but "sceptics" quote it as if the problem hasn't been addressed. I would have worded that sentence differently.
A Climate Myth about the Sun
No, variations in the energy output from the Sun are not causing the current climate change.
(1) Solar energy output appears to have remained relatively stable since the 1700s and has not been responsible for climate change.
Link:
https://www.iau.org/news/pressreleases/detail/iau1508/
That's from The International Astronomical Union, the expert international body in astronomy.
(2) What about later this century? A future grand solar minimum has been suggested as a potential cause of "global cooling". But. A GSM could see global average temperature rise trimmed by around 0.12C for the second half of this century - not a lot compared to the rise in temperatures coming from AGW.
My source is: "Regional climate impacts of a possible future grand solar minimum" - Ineson et al, 2015
(3) The Sun is a Main Sequence star, so it increases its energy output very slowly over time. In the Cambrian, over 500 million years ago, the energy output was about 5% lower than now.
With an increase in output of about 0.1% per million years, this has no connection with the current global warming of course.
http://www.geologywales.co.uk/storms/solar.jpg
Climate Myths about Ice Ages
A "sceptic" myth that appears quite often is "we don't need to worry about global warming - there's an ice age coming soon".
In reality, the Ice Age (the succession of glacial and glacial stages) might have ended, simply because CO2 levels are now too high. Glacial advances require CO2 levels to be quite low - in all the previous glacial stages of the Pleistocene "ice age", CO2 was under around 230 ppm.
CO2 was significantly above that (at about 270 ppm) even before the Industrial Revolution. With CO2 now around 415 ppm we are not likely to see a new glacial stage within any time we might be interested in.
https://www.carbonbrief.org/human-emissions-will-delay.../
Glacial inception requires summer temperatures in the northern hemisphere to be low enough for snow to build up year on year, starting mainly on north-facing slopes of mountain ranges. This in itself acts as a feedback - as the snow and ice covers an increasing area, it reflects more solar energy, reinforcing the cooling process.
While we are considering ice ages, what about the Little Ice Age?
None of the small-scale variations within the Holocene were as significant as the current change, which is a major disruption of the long-term carbon cycle. The Medieval Warm Period and the Little Ice Age were concepts that came out of relatively early climate research. Newer research suggests that we need to be careful about how significant they were.
I recommend "Frost fairs, sunspots and the Little Ice Age" - Lockwood et al, 2017
https://academic.oup.com/astrogeo/article/58/2/2.17/3074082
Climate Myths about Models in Climate Science
“This climate change, it's just all based on inaccurate computer models" - I've seen that so many times.
(1) Computer models are not the only basis for climate science. At the core of climate science there are some basic concepts in atmospheric physics discovered in the 19th century.
https://cdn.auckland.ac.nz/.../documents/inaugural_final.pdf
(2) Climate models that were run 50 years ago were pretty accurate in indicating where we'd be in the 2020s.
https://www.carbonbrief.org/analysis-how-well-have...
From the Conclusion......
"Climate models published since 1973 have generally been quite skilful in projecting future warming. While some were too low and some too high, they all show outcomes reasonably close to what has actually occurred, especially when discrepancies between predicted and actual CO2 concentrations and other climate forcings are taken into account."
(3) In the early 1980s, the fossil fuel corporation, Exxon, got its own scientists to investigate climate change, and the conclusions were the same as every other project.
They used their own model to show how the Earth was likely to warm in the future, and the predictions for the 2020s were remarkably accurate.
https://www.science.org/doi/10.1126/science.abk0063
" ...... we demonstrated that Exxon’s internal documents, as well as peer-reviewed studies published by Exxon and ExxonMobil Corp scientists, overwhelmingly acknowledged that climate change is real and human-caused. By contrast, the majority of Mobil and ExxonMobil Corp’s public communications promoted doubt on the matter. "
A Climate Myth about Volcanoes
No, volcanoes are not causing the current warming of the Earth. Human activity in burning fossil fuels produces over 100 times as much CO2 per year than all the Earth's volcanoes put together.
https://factcheck.afp.com/no-volcanoes-do-not-emit-more...
A Climate Myth about "Natural Cycles"
There are many "natural processes" that can cause climate change.
Obviously, scientists have investigated the possibility that the current change is caused by some natural process.
The Earth's temperature is a response to various factors, called climate forcings, such as changes in the gases in the air, changes in the Earth's orbit and rotation (which alters the amount of energy reaching the surface from the Sun), plate movements, ocean currents, and some others.
Here's a useful summary of these, produced by the British Geological Survey:
https://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html
Then to discover which factors are involved in the current warming we turn to attribution studies.
Here's one attribution study -
"Global temperature evolution 1979–2010" - Foster & Rahmstorf, 2011
...........we list the linear trend in the signals due to ENSO, volcanic forcing and solar variation in table 3.
The magnitudes of these trend contributions are quite small compared to the overall trends.
In fact the net trend due to these three factors is negative for all data sets except UAH, for which it is zero. Hence these factors have not contributed to an upward trend in temperature data, rather they have contributed a very slight downward trend
OK - so without human activity, the Earth would be cooling very very slowly, because the sum effect of 'natural' forcings is very very slightly negative.
All the other forcings have been investigated in this way, and the conclusions are the same.
