A primer on climate change science
A primer on the science of climate change
How I got involved
There is a lot of disinformation around when it comes to climate change, and I felt compelled to sit down and find out what I could about the facts. An online news letter sent out by Scientists for Global Responsibility (SGR) asked for someone willing to write about deliberate misinformation concerning a scientific subject, and climate change denial in particular. I am a member of this group, and as I knew where to find the relevant information, I sent the editor a proposal for an article that would begin with a short introduction to climate change. It was accepted, although I got told: “Don’t write about climate change, everybody knows what it is.”
So I concentrated on the way doubt has been cast on information regarding the harm certain substances are likely to inflict, data which would affect the bottom line of their providers. Examples include the effect of tobacco on health, acid rain and also climate change science. The upshot is that people no longer know what and whom to believe. It turns out that one particular marketing company had been directing such doubts, becoming incredibly adapt in doing so and reaping billions of dollars in fees in the process. Soon many pseudo-scientific climate-sceptic foundations got in on the act, largely funded by companies providing the damaging substances.
The editor then suggested I write – wait for it . . . - an introduction on climate change, and then I was asked to go into greater depth. I couldn’t admit I hadn’t got a clue, now could I? So I sat down gritting my teeth and read everything I could find out about the science, and subsequently enrolled for an online course, as it was so fascinating. This is the result:
Without the warmth of the sun, there wouldn’t be any life on earth at all, at least no life as we know it. Every square metre of earth receives about 288 watts of solar radiation. This consists of visible light, infrared light and some (luckily very little) ultraviolet light. Most of the latter is screened off by the ozone layer, otherwise plants, animals and people too, would soon burn to a crisp.
During the night this energy is radiated back into space in the form of infrared light. A small quantity of naturally occurring greenhouse gases, such as carbon dioxide and methane prevent some of the outflow of warmth, making the earth livable (and a good thing too!). As the scientist Tindall wrote back in 1862: “Without this gaseous vapour. . . . “the sun would rise upon an island held fast in the iron grip of frost.” The ‘gaseous vapour’ refers to water vapour. Later he discovered that carbon dioxide and several other gases also prevent the warmth from dissipating somewhere in space. However – that was ‘a small quantity' before human beings meddled with the Earth’s atmosphere.
Now you ask me: “Where did greenhouse gas come from so far back in time, before life existed or mammals such as us?” Initially most carbon dioxide (CO2) was produced by volcanoes, and then eventually CO2 was produced by primitive life forms, before more complex forms such as cows evolved. Marsh gas consists of methane, and I expect there were some marshes in the far and distant past. One of the answers is shellfish – the Guardian had an item about ‘flatulent shellfish’, apparently pumping out measurable quantities of methane and nitrous oxide very early on. Both are very potent greenhouse gases.
So these greenhouse gases – and there are about 30 known gases which behave in this way - absorb part of the outgoing warmth, locking it in the Earth’s atmosphere. Several of these such as water vapour dissipate in a day or so, some stay around for centuries on end, trapping heat; carbon dioxide (CO2), the best-known one, is quite long-lived. We have an excellent set of data about historical CO2 emissions. An early example is shown in the book ‘Air and Rain’ published in 1872 by Angus Smith and included a value of 327ppm from the top of Ben Nevis. Charles Keeling, an oceanographer and atmosphere scientist, began in 1958 to take regular measurements at an observatory on the top of Mount Mauna Loa on Hawaii, where the air is ultra-clear. These were continued after Keeling’s death and are still being collected (see website www.CO2.earth). As snow falls and compacts to form ice at the poles bubbles of air from that time are trapped, the amount of CO2 in the atmosphere from much earlier times can be measured by analyzing air from bubbles in ice cores, drilled from Greenland and Antarctic ice.
This data shows that t. he atmospheric carbon (or carbon dioxide) count has risen from about 280 in pre-industrial times to 327 in the 1870s and much, much faster since the 1960s to 408ppm in January 2018. During that time temperatures have also risen, but not quite as quickly.
Much of the CO2 as well as a lot of heat is absorbed by the oceans. Quite lot of CO2 is used by plants and trees and locked in as wood and peat. If this accumulates this will eventually turn to coal or oil. Some is bound up by weathering of rocks or other carbon sinks. However we are now burning oil and coal to release CO2 at far greater rates than natural systems can absorb. Temperature has risen by an average 0.9 degrees C, but by much more in the Arctic. Clearly, climate change in itself is a natural process; however, the speed with which it occurs currently, is not. The carbon dioxide emitted by burning fossil fuels and making cement, amongst other things, are due to the activities of human beings.
I mentioned some of the misinformation being bandied about. A notorious instance was the assertion that sunspots or solar flares are warming the entire solar system (and therefore the earth as well), and that it is not our own mistakes that are heating the earth. One of the reports made in 1991 to the International Panel on Climate Change (IPCC) shows that the upper atmosphere (that is the atmosphere upwards from about 50 km above the earth has cooled instead, while the lower part has warmed up. The career of the scientist responsible for this important new information was ruined by the efforts of those batting for vested interests. A website www.skeptikalscience.com created by a number of reputable climate scientists provides a refutation of most of the misinforming statements, explaining where they go wrong.
Until the mid-twentieth century the climate system was largely in balance, with vegetation able to use the carbon dioxide and release oxygen in its place (and we definitely want that!). According to scientific opinion a carbon count of 350 ppm would remain manageable and be back in balance, and that is what humanity should aim for. We personally are unable to remove the CO2 already emitted, which will be reflected in higher temperatures, greater sea level rise and more stormy weather. What we can do and are duty-bound to do, is not add to the climate change already in the pipeline by keeping our energy use as low as possible, in particular the use of fossil fuels – without making ourselves uncomfortable. Please don’t invest in fossil fuel companies – you may have heard of stranded assets, that is: they are bound to lose their value in a year or so anyway.
PS: By studying ice core data scientists know that the carbon count has been between 172 and 300 parts per million during the last million years. There have been ice ages and interglacial periods during that time. But during the last 10,000 years the temperature has been exceptionally stable, overall temperatures not changing more than by 1 degree C. with the carbon count below 280 ppm until the beginning of the industrial revolution. This climate stability enabled us to flourish. I just hope we will be able to continue to do so!