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🌍 Ask a climate scientist

Thinking fast and slow on climate

Part I: The climate system

Photo by Markus Spiske on Unsplash

Hey 👋 I’m Lucy, Earth Fund’s resident climate scientist! I’m here to answer your questions on climate change and help the Earth Fund DAO find planet-saving projects to fund!

Today, I’m writing part one of a post about why we need to think both short-term and long-term if we’re going to fight climate change.

We are pumping CO2 and other greenhouse gases into the atmosphere at a breathtaking rate.

We now know that we need to totally revolutionise our economy within a couple of decades.

That’s fast.

But climate change is also discussed as something that will have repercussion and need to be addressed for millennia to come.

That’s slow.

The different timescales that the climate crisis confronts us with can be hard to wrap your head around.

But when it comes to climate action timeliness must come front and centre.

So let’s get our clocks in order.

The climate system clock

The climate crisis is often characterised as a slow-moving catastrophe.

Glaciers melt at— well, a glacial pace — of 10’s of cm per year and the sea level is creeping up at an average global rate of 0.3 cm annually.

It has become a cliche to compare the two, but unlike Covid-19, it didn’t turn up at our doorstep just before Christmas and upend the lives of people around the world by Easter.

We have known about it for a while. (Longer than you might think from the present state of inaction in fact.)

We’ve known about the greenhouse effect since 1856

The greenhouse effect was discovered by the pioneering scientist Eunice Foote in 1856, and the recognition of the potential threats was firmly rooted in the scientific community by the 1970s.

With a bitter irony, it was the fossil fuel giants like Exxon and Shell who lead some of the earliest research.

But despite this early understanding, we still collectively thought about climate change as a problem for future generations. Something lurking far-off in the murky latter half of the 21st century, beyond the short time horizon we humans are good at thinking about.

Now: we’re starting to see the impacts

What has shocked both scientists and the public is how quickly and dramatically we are seeing the impacts of global warming.

Wildfires, heatwaves and floods are only going to get more common.

The raging wildfires, extreme heatwaves, devastating floods, droughts, and hurricanes have been occurring with almost numbing severity and frequency in the last few years.

Each year the tracts of forest and peatland set ablaze by wildfires is inconceivably greater than the last.

The one positive (if we could ever call it that) is that these extreme events have succeeded, where mountains of scientific evidence have failed, to relegate outright climate denialism to the dustbin of history.

There’s good reason scientists have struggled to predict these events.

While climate models are good at predicting ‘average’ system behaviour, they are not so good at predicting extremes. These are what are often referred to as ‘tail events’: in the bell curve of typical weather, these are way out in the fringes.

These extreme events are increasing in severity and frequency in tandem with the rising global mean temperature.

With climate change, what were once in a thousand year events have become once in a decade events.

Year on year we can expect more of these, and likely more surprises too, with further cascading impacts from crop failures to disrupted global supply chains and human migration, and the cascading, and incoherent, political implications these have.

Soon: things will get worse unless we act

So the impacts of climate change are happening now.

What happens in the coming decades depends on our mitigation efforts.

I will speak more to this in the next post, but I will say now that it is imperative that global emissions reductions start before 2030, and net-zero must be reached by 2050.

This imagining of the world in our lifetimes and that of our children assumes that humanity does rise to this challenge.

The industrialised world has been emitting greenhouse gases at a rate unseen in geological history. We have essentially shocked the Earth system. And like people, the climate system takes time to process and respond to shock.

While we are already seeing some of the impacts, the inherent lag in the Earth system means that some of the warming and other effects of the greenhouse gases we’ve already put into the atmosphere are yet to materialise.

What would happen if we stopped all emissions right now?

A useful way to think about this is to consider what will happen if we ceased all emissions of greenhouse gases and aerosols immediately.

The good news is that while temperatures will continue to creep up for a couple of decades, further warming would still likely be less than 0.5 C by the end of the century.

At that point, will have stabilised.

Other aspects of the climate system have greater inertia.

The cryosphere (that is the icy world of glaciers and ice sheets that adorn our high latitudes and mountains) in particular will take time to reach equilibrium with the higher global thermostat.

Think of an ice cube slowly melting at the bottom of a glass long after it’s been taken out of the freezer. As a result sea level rise (which in an optimistic scenario will already have reached 1 metre by the end of the century) will continue far beyond 2100.

Of course, we will not cease all emissions immediately.

As long as greenhouse gases are accumulating in the atmosphere we will continue to see impacts intensifying.

If we succeed in reaching net zero by 2050, that means impacts will continue to increase up to that date, and for several decades after that, the system will be readjusting.

But by say 2200 (the timing here gets fuzzy), some kind of new equilibrium may have been reached.

And whether that new equilibrium is a hospitable one or not depends on our actions.

In the post-net-zero medium-term, it is not just humans we need to consider.

It’s not just humans that will be affected by climate change.

In a 2 C warmer world, up to 18% of plants and insects could lose more than half of their climactically viable range.

Small hardy enclaves of threatened ecosystems may persist over the next few decades, but as we have seen over and over again, for fragmented and stressed populations extinction eventually becomes an inevitability.

Whole ecosystems are also at risk.

Particularly those that are unable to quickly migrate to cooler latitudes.

70–90% of tropical corals, which make up the skeleton of coral reefs, will likely disappear by midcentury.

So even after warming has stabilised global ecosystem dynamics will continue to shift.

This gradually shifting world order that I paint is of course assuming that we have not already set in motion some more destructive feedbacks such as the sudden release of huge amount of methane from thawing permafrost, or catastrophic instabilities in the Greenland or Arctic ice sheets.

Such instabilities would lead to very rapid warming and sea level rise — suddenly speeding up our climate clock.

Deep time: looking far ahead

And now for the longer yawn of deep time.

At this point, we stop talking in terms of human lifespans and instead in terms of the thousands and millions of years over which mountain ranges rise and fall.

In deep time, it is the irreversible or near-irreversible changes that we have to consider.

While some greenhouse gases such as methane break down quickly in the atmosphere, others such as CO2 has a residence time of hundreds of thousands.

This means that, in the absence of extraordinarily large-scale deployment of carbon removal measures in the medium term, what we have emitted will persist for a long time. A very long time.

Global warming would also be here to stay.

The loss of certain species and ecosystems is particularly important when we look forward to the deep future. This is truly irreversible.

As for other mass extinctions, new species will flourish in their place. But this time now will mark the turning point.

What we’re doing to the planet is not a minor blip.

It is major and epoch-defining.

Many of the changes, such as the increased atmospheric CO2 and ocean acidification are unprecedented in the past 65 million years at least.

The term the ‘Anthropocene’ — a geological measure of time where the Earth has been affected by mankind’s actions — has entered into the mainstream vocabulary for good reason.

I speak of the far-off geological future not as an invitation to bask in our own insignificance.

Quite the opposite.

It is to emphasise the magnitude of our actions.

Humans have become the major geological force on Earth.

We are fundamentally rewiring the geochemistry and dynamics of the planet.

Species have, and will continue, to go extinct because of us, and other species, and whole ecologies, will evolve and flourish in the new world of our making to come.

But we can spin this on its head: we have great power. And that should be empowering! We can and must change the planet’s fate.

Stay tuned! In the next post, I’ll consider what actions we can take now and in the medium term to make the planet a better, healthier place.

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Earth Fund is a global community of people working together to find and fund world-changing projects around the world. earthfund.io

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Lucy Tweed

Lucy Tweed

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