The phrase “+1.5 °C above pre-industrial” has become a mainstream fear tactic. It’s led to (most) people believe that a hotter world will bring extreme heat and seasonal weather variability, cause resource shortages, raise sea levels and drown coastal communities, increase the range of disease carriers, and so on. Life on Earth would become a lot more difficult in a warmer world. But the thing is, Earth’s current climate is relatively cool. Even if it warmed by 3 °C, it would still be rather mild. Why is this so?
Earth’s climate can be generalized into two types: hot house, and ice house. Ice house climates occur when there is significant permanent ice on the surface, such as now. Hot house climates are the opposite; there is no ice or nearly none, such as the time the dinosaurs lived.
The picture above shows all the times Earth was an ice house. The world has been a hot house for far longer than it has an ice house, and we know that life survived through all hot and cold cycles. So what’s the real problem with climate change? Won’t life be able to adapt again?
There are two problems that are commonly misunderstood: rate and unevenness.
Global warming speedrun
A temperature increase on its own isn’t the end of the world, and we can check the geological record for evidence. A great example of a previous warming event is the PETM (Paleocene-Eocene Thermal Maximum). This is a global warming event that occurred about 55 million years ago. In less than about 50 000 years, global temperatures rose by up to 8 °C.
During the PETM, the ratio of biological carbon (12C) to non-biological carbon (13C) suddenly increased. This means that a lot of carbon that was once in living things was suddenly released into the atmosphere and increased the ratio.
Explaining 12C and 13C
Every atom is composed of 3 smaller particles: the proton, neutron, and electron. These are called subatomic particles.- Proton
- A positively charged particle. The number of protons defines the atom. For example, hydrogen atoms always have 1 proton. Carbon atoms always have 6 protons. Oxygen atoms always have 8 protons. There is no exception to this rule
- Neutron
- Neutrally charged (ie. no charge). Atoms can have different numbers of neutrons, and that number determines the isotope of the atom. If a carbon atom has 6 neutrons, it is carbon-12 (12C) (6 protons + 6 neutrons). Carbon with 7 neutrons is carbon-13 (13C) (6 protons + 7 neutrons). Carbon-14 (14C) has 8 neutrons, and so on
- Electron
- Negatively charged particle. Orbits the atom’s nucleus, which holds the protons and neutrons. Not important for this explanation
- Isotope
- Think of these like different versions of the same atom. 12C, 13C, and 14C are all isotopes of carbon. 16O, 17O, and 18O are all isotopes of oxygen. 2H is an isotope of hydrogen. Remember, the number of protons is the same for any given atom
Not all isotopes are equal. When you count carbon atoms in the universe, nearly 99% of them are 12C. The remaining 1% is 13C, and a trace amount is 14C. Therefore, any object with carbon in it will have a similar distribution to the one above. However, living things don’t have the same carbon ratio; life prefers 12C over 13C.
This means that if you look at the distribution of carbon in an organism, it will have more 12C than 13C, relative to a rock that has never been part of an organism. Maybe 99.5% 12C instead of 99%. So going back to the PETM increasing the ratio of 12C to 13C, this means that a lot of biological carbon must have been emitted. In other words, combustion of organic materials like coal and oil.
The emitted carbon must have been gaseous, so very likely carbon dioxide; a greenhouse gas. Therefore, we can use the PETM as a proxy of what happens if we keep burning fossil fuels for a very long time.
The problem though, is that the PETM happened over 50 000 years. Assuming an anthropogenic temperature increase of 1.2 °C in 200 years, that’s a rate 37.5 times faster than the PETM. And that’s where the problem lies.
The PETM had mixed results on life. On one hand the biosphere was able to adapt as a whole. Forests were at the poles, and it was the era when our primate ancestors evolved. On the other hand, there was a big extinction event among many marine species at the base of food webs. The oceans were as hot as hot springs and they became acidic.
Go back another 200 million years to the end-Permian mass extinction, where somewhere between 70 - 80% of all species died off. The suspected cause for this armageddon was massive volcanic eruptions. It caused a spike in CO2 levels, a 8 - 10 °C temperature jump, ocean acidification, circulation disruption, anoxia (no oxygen) and euxinia (H2S). These volcanoes erupted for about 2 million years and have an upper bound estimated emission of 1.2 × 1013 tonnes of carbon. Compare that to our modern emissions (3.5 × 1010 tonnes/year), which is about 600 times faster. That’s an alarming rate.
To creatures which live for 70 - 80 years, the global temperature rising by 1.5 °C in 200 years is slow. But geological time is very very slow. Ten thousand years, roughly the length of all modern human history, is literally an instant to the Earth. Life can adapt to increased temperatures, it has done so many times already; but it needs millions of years, not hundreds.
Warmer = more energy
The second problem of climate change is people misunderstanding what a “global average temperature” really means. “Average temperature” sounds like a nice and simple metric but it’s misleading to the average person. Kind of like having a group of one millionaire and some homeless people, then saying the average income is about $100K.
The Earth is never equally warm everywhere. Half of the planet is always facing the Sun and the other half is always facing into dark space. The energy received from the Sun isn’t all equal, it’s weaker at the poles where the surface curves away. Uneven heating means there is always a temperature/energy gradient across the planet, driving the winds and ocean currents. Then add in geographic features such as mountains which disrupt air flow, forests which absorb heat better than deserts, or ice which reflects a lot of heat than water, and the Earth becomes a giant system with constantly changing energy densities in the atmosphere and oceans.
Thermodynamics 101
Finally I get to actually use some university knowledge.- Flux
- In heat transfer, this typically means the rate of energy passing through a unit of area
The most important rule about thermodynamics you need to know for this article (and for thermo in general) is that energy always flows from hot to cold. The universe is always trying to reach the same temperature everywhere. Hot things cool, cold things warm. The difference in temperature between two points is called a temperature gradient. Given enough time, any isolated system (a volume of space that has stuff inside it) will have the same temperature everywhere. This state is called thermodynamic equilibrium, or thermal equilibrium. The bigger the temperature gradient, the faster the heat transfer. If you isolated the Earth for a quadrillion years with no Sun, it would have the same temperature everywhere and reach thermodynamic equilibrium.
As energy flows from hot to cold, it can do work. You can think of work as any process that happens as a result of flowing energy. For example:
- Warm air moving around the Earth causes the wind to blow
- Hot steam expanding and cooling can rotate a turbine and generate electricity
- A fire releases energy in chemical bonds of fuel as heat, which can boil water
The important thing is that without the flowing energy, none of the examples above would occur naturally. Water never boils on its own and wind doesn’t blow without a temperature/pressure gradient. Without flowing energy, no work is done (nothing happens).
The thermo lesson ends here in case things keep getting more confusing (it can get a lot uglier, trust me). The point is, energy moves from hot to cold. The flow causes things to happen.
A better way to quantify warming is with energy. After all, temperature is just an average measure of energy, so in theory we can calculate the total energy that the atmosphere holds. In practice, this is basically impossible. But we can still do a qualitative thought experiment.
Heat distribution across the planet is convective because water and air are fluids. In convective heat transfer, the heat flux is proportional to the temperature gradient/difference. The bigger the gradient, the stronger the flux, ie. more energy flows at once. More energy flowing means more work can be done. Like boiling a pot of water faster with a stronger fire, more intense energy transfer should result in stronger winds and ocean currents. In other words, more storms and intense weather events.
The Earth is a very complex multivariable system and it is impossible to model its behaviour with an idealized high school-level equation, but the core principles stand. The uneven energy distribution on the planet drives weather. More unevenness means stronger forces. More energy raises temperatures, which means things happen faster.
Takeaways
The main point of this article is the explanation of some climate change problems that people are less familiar with. I didn’t mention the actual consequences of a temperature increase, potential feedback loops, or other gloomy news. We’ll see what really happens to the world in a few decades.
Don’t get me wrong, I think climate change is real and a big temperature increase is bad (and incoming). Our world is too dependent on petroleum products and I don’t believe the hype of EVs and being “carbon neutral” will save us. Will the future be a movie-like doomsday scenario? Probably not. But it also probably won’t be a pleasant one either. I would learn how to grow crops at this rate, you never know if the next Great War happens because of a resource conflict.