If you already understand the science of climate change, in this video I’m not going to tell you anything that you haven’t already heard a thousand times. And if you’re a climate change denier, I’m not going to tell you anything that you haven’t already ignored a thousand times. No, this video is dedicated to all of you who are in between. What is climate change? Should we be worried? And could it wipe out all of humanity?

This is the second episode of AltruPhysics dedicated to the so-called existential risks. In other words, the dangers that are capable of bringing about our own extinction, or of creating a world simply not worth living in. Examples of these risks are pandemics, nuclear wars and… climate change?

Before drawing any conclusions, let’s try to understand what climate change actually is first. And at the end of the episode we’ll clarify if it really is a risk that we should be worried about.

Natural climate change

The Earth’s climate is constantly changing and there are many different reasons why. For example, the Earth’s orbit around the Sun varies over periods of thousands of years, the Earth’s axis of rotation changes its direction periodically, and even the energy emitted by the Sun oscillates.

All these astronomical phenomena cause great changes in the Earth’s climate, such as ice ages, and there are also other natural phenomena, such as volcanic eruptions, that can both warm and cool the planet.

But are these the kinds of changes being referred to in the news whenever they mention climate change?

No, these astronomical changes occur over periods of tens of thousands of years. And volcanic eruptions have been happening for millions of years. On the other hand, the type of climate change being talked about so much today is a phenomenon that began relatively recently, at some point during the 19th century.

Let’s talk now about anthropogenic climate change, that is, climate change which is caused by human action.

Anthropogenic climate change

Burning coal is a simple way to get energy. In fact, we’ve been burning coal for over 3,000 years now. But it wasn’t until the late 18th century that Britain began to discover the enormous benefits of coal, which led to the start of the Industrial Revolution. And a large part of the global economic and technological progress that we enjoy today is due to our friend Señor Coal. But this friendship turned out to be a betrayal.

Burning coal, like burning other fuels, releases greenhouse gases. In other words, gases that, by becoming concentrated in the atmosphere, allow solar radiation to reach the Earth’s surface, but make it difficult for part of that heat to escape back into space, creating an effect similar to that of a greenhouse.

In fact, we can see how the average temperature of the Earth has been increasing little by little in the last hundred years.

And the concentration of greenhouse gases in the atmosphere, such as carbon dioxide (CO2), methane or nitrous oxide, have also been growing.

But of course, simply looking at these two curves we cannot conclude that one is a consequence of the other. It could be pure coincidence. However, these and many other measurements, along with decades of research, have led thousands of scientists around the world to an unequivocal consensus: This correlation is not coincidental, it is causal.

In other words, the burning of fossil fuels such as coal, natural gas or oil, as well as other industrial and agricultural processes, produce greenhouse gases. And these gases cause, among other effects, the increase in the average temperature of the Earth.

If you’re not convinced, here’s 2400 pages showing results from thousands of experts on the physical basis of climate change, according to one of the reports by the Intergovernmental Panel on Climate Change (IPCC), which is the most cited, complete and reliable source on the subject.

But if you’re short on time, you can take a look at this 32-page summary. There’s one graph in particular that I find very illustrative, where the temperature increase predicted by two simulations is compared: One in which there are no humans (but there is natural climate change caused by phenomena such as the sun and volcanoes), and another simulation including humans. And it turns out that the temperature increase that we observe in the real world fits the second case very well.

In other words: Everything indicates that human beings are the main cause of climate change.

Still, one might think that the Earth is huge and has been around for billions of years, so a few decades of industry can’t have had such a big impact. After all, as I said before, volcanoes have been emitting tonnes of CO2 for millions of years. Is our contribution really that important?

Well, surprisingly, yes. It has been possible to estimate the concentration of CO2 in the atmosphere for hundreds of thousands of years. And you can see that for millennia there have been oscillations around a certain mean value. However, in the last hundred years, the concentration of CO2 in the atmosphere has shot up to almost double that value, and it doesn’t appear to be stopping.

There’s a lot more data that you can consult related to climate change. But now let’s talk about what really concerns us. Are a few extra degrees really so important?

Should we worry about a few more degrees?

Every time climate change is spoken about, an “increase of 1 or 2 degrees Celsius” comes up too. This number refers to the average temperature of the Earth’s surface with respect to the pre-industrial average temperature, which means that of the second half of the 19th century.

But I grew up in the south of Spain, and I know that whether it gets up to 40 degrees or 42 degrees there isn’t really a huge difference: You’re going to roast either way. So a few extra degrees shouldn’t scare me. Right?

Careful! Those 1 or 2 degrees are a global average. It’s not that the temperature of each region on Earth will rise by 1 or 2 degrees. There will be areas that won’t be affected, areas where the temperature will even drop, and others where the temperature will rise much, much more. In fact, 70% of the planet’s surface is ocean, which usually has a fairly stable temperature, whereas on dry land the changes are much more extreme. In fact, in the northern hemisphere, where there is a greater proportion of land, the temperature has already increased by around 1.4 degrees.

That said, and oddly enough, a temperature rise of just 1 or 2 degrees does have a huge impact on nature.

How does climate change affect nature?

Life on Earth is the result of billions of years of evolution, and nature is a very complex system, adapted to certain environmental conditions. Even small changes in temperature can greatly alter entire ecosystems. A few degrees more can change migration patterns, distribution and the diversity of species. Disturbing the ecological balance leads to irreversible changes, such as the loss of habitats or species extinction.

And it doesn’t end there: Of all this excess CO2 being emitted by human beings, more than 25% is absorbed by the oceans. This causes them to become more acidic, which affects marine life and biodiversity. To make matters worse, as the temperature of the ocean increases, its volume increases too, and ice in areas such as Antarctica and Greenland starts to melt, causing the sea level to rise.

On a personal note, one of the most unforgettable experiences of my life was visiting Australia’s Great Barrier Reef, a wonder of the natural world and of great scientific interest. Unfortunately, to this day, more than half of the coral has already disappeared. And it is estimated that a rise of 1.5 degrees can kill all the remaining corals on Earth.

But when talking about 1, 1.5 or 2 degrees, it might seem like something special happens when you get to those figures. In reality, they’re totally arbitrary numbers. A 2 degree rise is worse than a 1.9 degree rise, and a hell of a lot worse than a 1.5 degree rise. So each additional tenth of a degree means a worse world, and a harder challenge for humanity to solve.

Well, unfortunately, given our current global policies, we’re not heading for an increase of 1, or 2, but of 3 degrees. What will happen to humanity then?

How will climate change affect humanity?

In the near future, there will be areas where human beings simply will not be able to live, and I’m not just talking about it being very hot. Extreme events such as droughts, torrential rains, heat waves or fires will become more intense and more frequent.

To give a couple of recent examples: This year, 2023, the wildfires in Canada have started earlier than normal, and have burned a larger area than any other year on record. And this is already the case despite us being just half way through the year.

But without travelling any further, this month we have witnessed historical floods in Zaragoza. Unfortunately, these types of “records” are just going to become more and more common.

And that’s not all. As the frequency of extreme events increases, the likelihood of two or more extreme events occurring in the same place at the same time increases, making it more difficult to cope with and recover from them. For example, a drought at the same time as a heat wave, or a famine at the same time as a pandemic.

Speaking of pandemics, some diseases will become more common and spread to new parts of the world. For example, mosquitoes that transmit dengue or malaria will be able to survive in new latitudes. And many countries will not be prepared to deal with diseases never seen before.

Rising temperatures, droughts and torrential rains will, of course, also affect agriculture. So much so that in some regions it will not be possible to produce food, nor will there be human beings capable of supporting these conditions to work in the fields. And without water and without food, the only option is to emigrate.

And to these people emigrating we should add all those who will escape from coastal areas at risk of being flooded. (Here’s an interactive map where you can see an estimate of how the sea level will rise year after year).

So we will have tens of millions of climate migrants. And it is possible that you and I are among them. And these waves of immigration will bring increased competition for resources, political instability, and wars.

All this will have a huge and irreversible negative impact on the world economy, and its corresponding cost in human lives and many other animals.

To make matters worse (and to demonstrate that karma truly doesn’t exist) those who will suffer the most from the consequences of climate change will be from the poorest countries, which are the ones that have contributed the least to the problem.

In general, the world could become a much worse place to live. And I’m not talking about the distant future. All these problems, and many more that I haven’t mentioned, have already begun to manifest themselves, and may be a daily reality in 2050: The world that the children of today will inherit.

But as dystopian as what I have told you may seem, this is just the tip of the iceberg.

Can climate change wipe out all of humanity?

So far I’ve mentioned what could happen if the temperature rises by a few degrees. But what about if it keeps rising even higher?

One terrifying possibility is that so-called tipping points are reached. In other words, when rising above a certain temperature, a phenomenon is unleashed that causes the temperature to rise further, aggravating that phenomenon, and so on, in a vicious circle.

An example of one such tipping point is the melting of the Arctic permafrost. The permafrost is a frozen layer of earth which, when the temperature rises, melts and produces greenhouse gases, thus causing the temperature to rise even more.

We know of several of these tipping points. And in the worst-case scenario, they could lead to a temperature rise above 13 degrees, which would be an unprecedented humanitarian catastrophe. But luckily, according to IPCC predictions, such an extreme change in our climate, capable of directly causing our own extinction, is unlikely.

Even so, as I mentioned before, a rise in temperature of just 1 or 2 degrees increases the risk of pandemics, wars between great powers, or even nuclear wars, which, as I said in a previous episode of AltruPhysics, are indeed existential risks.

Therefore, climate change, even indirectly, could wipe out all of humanity.


If you’ve reached this point, thank you very much for your time. Maybe you haven’t believed anything I’ve told you about climate change. Or on the contrary, you might feel a deep sense of despair and think that we are all doomed.

In both cases, I hope you change your mind as soon as possible. Since in the end, both denial and pessimism lead to the same result: Doing nothing. And that’s just what we have to avoid.

Climate change is real and scary, but we are not doomed, and we have a lot to do. But I’ll talk about solutions in the next episode, in which I’ll explain the most effective individual actions to fight climate change. So I invite you to subscribe and hit the bell so you don’t miss it. And I hope to see you soon, in the next episode of AltruPhysics.