I've recently started taking Michael Mann's excellent Climate Change: The Science and Global Impact course on edX. This is my attempt to synthesise everything I have learnt in module one of that course as well as some other useful information about climate change.
By the end you'll:
My hope is that there is enough information in this blog post for you to give a 5-minute presentation on this topic.
It can be a lot to take in, there are false yet realistic sounding counter-arguments and disinformation everywhere. I'm going to try to break the core arguments down into easy to digest and regurgitate chunks.
First, let's make a distinction between climate and weather.
What we are seeing is the climate changing over time, it's currently 1 degree hotter on average than pre-industrial times and that has a lot of people worried.
Over the last 30+ years, climate scientists have understood more about what's happening, what's causing the climate to change, what impact it's having on the planet and the humans, plants and animals living on it.
Before we get to that we need to talk physics, I'll keep it short.
The thing to understand here is that light and heat are the same thing, they are part of something a lot bigger, and that's called the electromagnetic spectrum. What we can see, visible light, is electromagnetic radiation that resonates in the range of 400–700 nanometers (nm). What we feel as heat is electromagnetic radiation resonating at about 750 nm to about 10 micrometres (μm), infrared radiation.
A nm is smaller than a μm, so we call light shortwave radiation and thermal radiation (heat) longwave radiation.
The Sun is hot, hot things radiate energy at short wavelengths. To us that short wave radiation is light, at even shorter wavelengths it's ultraviolet light which we can't see. If sunlight was a sound, it would be a high pitched whine.
When that shortwave radiation hits something cooler, the cool thing absorbs the high-frequency shortwave radiation, turns it into a lower frequency longwave radiation and sends that back out. That longwave radiation is thermal radiation, i.e. heat. If heat was a sound, it would be a deep bass.
That's a really complicated way of saying, "When sunlight hits something cold, it makes it hot".
The first law of thermodynamics states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another.
The light energy hitting the Earth is not destroyed. Its changed from a higher frequency in the electromagnetic spectrum to a lower frequency, i.e. thermal radiation also knows as heat.
The Earth is round, so all of it doesn't get the same amount of energy at each point. The equator receives more the poles get less, and there are more complex effects like some of the Earth is more reflect-y than the rest (e.g. the ice-caps). This energy imbalance needs to be balanced, that's the weather that you see. The weather is the moving of energy around the planet.
So now we have a little understanding about light and heat energy, let's talk about Earths Energy Balance.
The Sun sends a lot of energy to the Earth, about 173,000 terawatts, compare that to all of the energy that humanity generates which is only about 18 terawatts of energy.
The enormous size of the energy the Sun is throwing down at is us is also why people are excited about the place solar power has in the climate solution.
The Earth receives about 340 watts of energy on each M² of the surface that's facing the Sun. That's enough energy to power about nine 40 watt light bulbs or one high power hairdryer.
The Earth will always find a balance between the energy coming in and the energy going out. The energy coming in is not getting destroyed, it's getting changed into another form and heading back out into space. This balancing act is called Earths Energy Balance.
Part of that equation is the temperature on the surface of the Earth, if to balance that equation it needs to increase the temperature, it will. The equation gets balanced, that's just physics.
We don't need a significant wobble in that balance to have a big impact on humanity. The energies going in and the energies going out are huge, and the temperature range at which life is comfortable on the surface of the Earth is slim.
In the case of Venus, it found its balance when the surface temperature reached 800 degrees centigrade. However, the black body temperature of Venus is just 54.5 degrees. "Black body" refers to the theoretical temperature on the Surface if Venus was a perfect black sphere with no atmosphere. The reason Venus is 800 degrees on the surface instead of 54.5 is because of the effect of the atmosphere and precisely the fact it's 97% made up of Carbon Dioxide, a Greenhouse Gas (GHG).
You can find a lot more information regarding Earth Energy Balance here https://earthobservatory.nasa.gov/features/EnergyBalance
Oxygen & nitrogen are mostly transparent to both the incoming shortwave radiation from the Sun (light) and the longwave radiation from the Earth (heat).
Water Vapour, Carbon Dioxide, Methane, as well as several other trace gases are greenhouse gases (GHG). This means they absorb the thermal radiation from the Earth and reflect it back out in all directions, some upwards and some back down toward the planet.
Now that we think of light and heat as the same thing but on a spectrum, it makes it easier to understand what's going on.
Water vapour absorbs energy across the spectrum. Still, there is a window in the middle, a range of longwave radiation that it doesn't absorb. So although it absorbs a lot of the heat coming from the surface of the Earth as that energy bounces around it moves down the spectrum until it hits that window and it's got a straight shot into space. That window is our energy escape hatch.
CO2 absorbs some of that energy but at different wavelengths to water vapour, between 12 - 15 μm. That range annoyingly fills part of the gap in our energy escape hatch.
The more CO2 we pump into the atmosphere, the more we are closing our energy escape hatch.
We would need some GHG in the atmosphere, in fact, if there were none the Earth would be about 33 degrees cooler than today.
We are releasing so much GHG into the atmosphere it's disrupting Earths energy balance, and the equation is balancing itself out by raising the temperature on the surface of the Earth.
Let's examine a couple of counter-arguments put forward by climate deniers that climate change is man-made.
There is some variation in the amount of energy the Sun sends out over time, we believe this is not the cause of the recent warming because of two reasons:
Yes, CO2 concentrations in the atmosphere have been increasing and decreasing over millions of years.
But since 1800 it's been increasing at a much faster pace, now it's the highest it's been for 800,000 years.
The last time the Earth had this level of CO2 in the atmosphere was 2.6 to 5.3 million years ago in the Pilocene era when there were trees growing on the south pole.
We are not destroying the planet, Earth will live on long after we are all dead. We are disrupting the energy balance, which is changing the climate and leads me to my next point.
Earths climate has been changing for a long time. Typically the Earth goes through long ice ages (~90,000 years) and short interglacial warm periods (~10,000 years). We are currently in a warm interglacial period.
The Earth spins on an axial tilt, and that tilt slowly changes over 100,000 years, we call this procession. This results in slow natural changes in the amount of solar radiation different parts of the Earth receive over time, causing ice ages and warm periods.
It takes a few thousand years for an ice age to form and a few thousand years for an ice age to an end, they happen slowly. Yes, the climate has changed throughout history but usually very slowly.
Life naturally adapts, animals migrate, plant species may slowly move across continents as the changing climate makes areas more suitable to their needs.
Sometimes, the climate changes very fast, when that happens, life can't adapt soon enough and there are mass extinctions.
For example, the great dying of 252 million years ago, where 96% of all marine species and 80% of all terrestrial species died. This happened possibly over only a few hundred years. The cause was massive amounts of CO2 being released into the atmosphere from sudden volcanic activity, causing temperatures to rise by 10 degrees.
The problem isn't climate change, it's climate changing too fast. Too fast for animal and plants to adapt, too fast for human society to adapt. There are seven billion people on this planet, all expecting an environment to remain mostly static. Depending on resources which we are not sure are going to be there in the future. Living in places where life is going to become much harder in a short space of time.
There has been a lot of study on this subject.
A great source of information on this is Carbon Brief. Specifically, the interactive guide called The impacts of climate change at 1.5C, 2C and beyond. I recommend you browse that site, it has condensed 70 research papers on the subject and presented it in an easy to understand format.
Many pages are shocking, but for me, the most compelling is this one:
It's the percentage of animals and plants that lose 50% of their climactic range at different temperatures. At 1.5 degrees centigrade, the percentage is in the single digits, at 2 degrees it creeps up into double digits, at 4.5 degrees we are in the high double digits.
The Earths energy balancing act is incredibly complex and has rebound effects. For example, as the temperature increase reduces the amount of ice on the polar caps, this, in turn, reduces the amount of sunlight that is reflected back out and therefore increases warming even more.
Climate change is non-linear. Pumping out 1% more GHG will not result in a 1% temperature increase, a 1% temperature increase will not result in us being 1% worse off.
It's not going to be a gradual worsening, it will have periods of things getting a lot worse quickly, following by periods of things getting worse slowly.
In terms of effects specifically on humanity, we have a few guesses, the first is that there is going to be mass migration.
As I said earlier, it's not about climate changing, it's about climate changing too fast.
On the timescale we are talking about now, decades, animals and plants will die, resulting in species loss. We also expect a mass migration of humans due to climate stressors such as rising sea levels, adverse weather & desertification.
Some of that migration will happen internally within a country, some will occur across countries. Immigration is a contentious topic even today, people displaced due to the horrors of war earns less sympathy than it used to.
Imagine one billion people who need to be relocated, who's going to look after them? Will you welcome them into your country consuming your resources?
What's certain is there going to be a disruption to the world order. The hope is that humanity answers the call to action and band together to look after those most affected, the fear is the rise of climate fascism.
"The only thing worse than a far-right racist movement that denies the reality of climate change is a far-right racist movement that believes in climate change" - Naomi Klein
Climate Fascism, or Ecofascism, is a far-right ideology which uses the climate crisis and ensuing mass migration as an opportunity to re-order society along their preferred racial lines.
Five years ago I would probably have laughed at that idea, but with the rise of the far-right across Europe and the post-truth nature of society these days it's becoming easier to imagine right-wing political parties using mass-migration, disruptions to the normal functioning of life as reasons to fan fears and win populist support.
All of this change leads to conflict and perhaps war, lots of war. This isn't just conjecture on my part the US military contractor Raytheon admitted in a candid interview with motherjones in 2013:
"expanded business opportunities are likely to arise as consumer behaviour and needs change in response to climate change."
"the company also expects to see demand for its military products and services as security concerns may arise as results of droughts, floods, and storm events occur as a result of climate change."
I suppose as a military contractor, you have to be honest about these sorts of things, it's your business after all, but seeing a company plan to make money out of the pain and hardship caused by climate change is unsettling.
Our goal is to keep the temperature increase since pre-industrial times to under 2 degrees, ideally 1.5.
The 21st COP meeting, COP21, happened in Paris in 2015, a year after the last IPCC assessment report. In this landmark meeting, 195 states agreed to the first universal and legally binding global climate deal aimed at keeping the temperature increase since pre-industrial times to under 2 degrees, ideally 1.5. We call this the Paris Climate Agreement.
The two parts of the agreement that are legally binding are:
NOTE: $100bn is just 8% of worldwide military spending per year.
Where the deal falls short is the emissions targets will be determined by countries themselves and are not legally binding. Besides, countries like the USA, which initially signed under the Obama regime, are failing to honour their agreement under Trump. The USA produces 20% of the worlds GHG emissions and yet has only 4% of the population of the world.
Unfortunately, we are not on track to meet either of these targets. We needed to immediately start reducing the amount of pollution we pump out every year instead we are still increasing by 5% every year. If we had started in 2010, we would only have had to reduce our emissions 3.3 percent each year to reach 1.5 degree target. Because of our inaction, we now have to reduce global emissions 7.6 percent each year between 2020 and 2030 to meet our goal.
In 2019 the UN released an Emissions Gap Report which concluded that if things continue as they are we may reach as much as a 3.2 degrees rise by the end of 2100.
Being Green is not a question of survival, perhaps a lot of plant and animal species will become extinct but our species will survive.
Being Green is a question of what type of world you want to create for the future, for your children. A world better than the one you were born into or much worse.
I'll leave you with a quote from Emma Marris in her New York Times opinion piece "How to Stop Freaking Out and Tackle Climate Change"
There is no threshold that means that it is too late or that we are doomed. The lower, the better. It is always worth fighting. Imagine dense but livable cities veined with public transit and leafy parks, infrastructure humming away to remove carbon dioxide from the atmosphere, fake meat that tastes better than the real thing, species recovering and re-wilding the world, the rivers silver with fish, the skies musical with flocking birds.
This is a future where the economic inequality, racism and colonialism that made decades of inaction on climate change possible has been acknowledged and is being addressed. This future is still possible. But it will only come to pass if we shed our shame, stop focusing on ourselves, join together and demand it.