Obligatory photo of a polar bear on melting ice

Climate change is coming to dominate the debate; it’s on the tip of everyone’s tongue. People talk. Be it extreme weather events or activist groups such as Extinction Rebellion (who took to the streets in the act of “civil disobedience”), the once distant and far off vision — the one that was supposed to affect our grandkids — is coming for us.

Views are polarised, as with everything these days. One side predicts the apocalypse, seeming hysterical to much of the public, who accept climate change but are dubious of its severity. The other side denies anything is even wrong, or that it’s either natural or nothing to be worried about.

Too often do people throw their hands up in despair — “Oh, — I don’t know about all this, I’m not a climate scientist”. Even at the highest reaches of the debate, science is thin on the ground. No wonder the sceptics do good business. Climate scientists haven’t transferred their knowledge to the public in the same way that say doctors do. So, people are wary of climate disaster, but they’ll trust the doc who tells them, sadly, they have cancer.

Great speakers such as Stephen Schneider (who passed away in 2010) have left vacant positions. And so, we’ve concluded climate science is hard, too esoteric. That might be true at the fringes (the bleeding edge), but the basics are so simple they’re taught in every high school physics textbook. We’ve known the science of the greenhouse effect since the 1820s!

No more shying away from the debate, or giving vague feelgood answers. We’ve got to have our arguments bolted to our hip. We have to win this. We don’t have a choice.

So, here are seven key points everyone needs to understand about climate change.

1. CO2 Heats the Atmosphere

Carbon dioxide doesn’t quite have the scare factor of hydrochloric acid or uranium-232. CO2 sounds boring. But without CO2 life on earth could not exist. It would be freezing for a start. Ice sheets would stretch as far south as New York City, and global temperatures would be 15.5 degrees Celsius lower [1].

All because of CO2. Perhaps not so boring after all.

CO2 is one of many greenhouse gases. It lets in shortwave radiation (visible and ultraviolet light) from sunlight which passes through the atmosphere. The earth absorbs the energy and radiates it back towards space in the form of longwave radiation (infrared light, e.g. heat — when metal is heated it glows red because the infrared light is bleeding into the visible spectrum). Greenhouse gases absorb the energy. Thereby warming the earth, just like glass in a greenhouse, hence the name.

In 1861, John Tyndal identified CO2 as a greenhouse gas capable of absorbing heat rays [2], and our knowledge has only deepened [3] [4] [5] [6]. The physics is foundational, and for it to be wrong would mean an awful lot of basic science is wrong as well. Perhaps, but it seems unlikely.

2. Carbon Dioxide is the World’s Thermostat

CO2 warms the earth. Therefore, if we increase CO2, the world will warm. The question is, how much? CO2 makes up only a fraction of the atmosphere at 0.04% [1]. Oxygen and Nitrogen make up the bulk. But these gases do not absorb infrared light, only the greenhouses gases do. Therefore, if only a small fraction of the earth’s atmosphere is receptive to infrared light, even small changes in these gases can have outsized effects relative to their concentration.

We understand this in our everyday lives. A cup of coffee won’t kill you, but twenty cups might give you a heart attack, whereas a drop of arsenic is deadly. It’s just more potent.

How potent is CO2?

Well, CO2 is responsible for between 9–26% of the earth’s greenhouse effect, depending on the cloud cover. Surprisingly, water vapour and clouds are responsible for between 36–72% [7]. That’s because the best way to increase atmospheric water vapour is to turn the temperature up (as every visitor to a sauna knows), and CO2 is the method of warming. It increases the amount of moisture in the atmosphere, raising temperatures further. If we discount the effect of water vapour, CO2 accounts for 80% of the greenhouse effect. [8]

Carbon dioxide is the world’s thermostat.

3. Fossil fuels = CO2

They’re called fossil fuels for a reason. Over millions of years, plants extracted CO2 out of the atmosphere and emitted oxygen via the process of photosynthesis. Millions more years passed and by various geological processes this dead plant matter, whether from land or sea, compacted and condensed till we got the fossil fuels we know today.

Burn that ancient carbon, and a simple chemical reaction occurs.

C + O2 = CO2

It’s that simple. Sceptics will readily point out humans release only 3% of the world’s CO2. But they’ve missed the point. The rest of the CO2 that is released is natural (from processes such as decomposition, respiration, ocean degassing, and volcanic eruptions), and for tens-of-thousands of years has been balanced with the CO2 absorbed. But now, we are tipping the balance.

Picture a bathtub. Every minute, 10 litres of water goes in, and through the plughole 10 litres of water leaves. Whatever the level in the bath, it will remain constant. Now imagine we turn the tap, so 10.3 litres of water enters the tub. Slowly and surely the water will rise as more water enters than leaves. The bath will inevitably overflow, the question is when.

Measurements from the Mauna Loa observatory in Hawaii show increases in CO2 from less than 320 ppm (parts per million) in 1960 to over 400 ppm today [9]. A truly whopping amount. It’s not surprising; we are emitting in decades what nature took millions of years to extract. And we are accelerating. In the 1960s, we put 0.6 ppm per year into the atmosphere, whereas the past decade has been closer to 2.3 ppm per year [9] [10].

The water in the bath is rising, but what happens when it overflows?

4. This isn’t New

Some ask, what’s the worry? CO2 will be a boost to plant growth, and a warmer planet is better than a colder one. I wouldn’t mind living near a sunny beach. Well, is this accurate?

Current CO2 levels are the highest for 3 million years, back in the Pliocene era, when levels were around 356–410 ppm. The continents were in roughly the same place, as well as oceanic currents — a snapshot into our future. Scientists found temperatures were significantly warmer. The average global temperature was 3–4 degrees Celsius above pre-industrial levels. Sea levels were 25 m higher [11]. Temperatures at the poles rose more extremely than anywhere else, 11–16 degrees Celsius warmer. Amazingly, explorers discovered fossilised beech leaves from this period in the Transantarctic mountains [12].