What will survive global warming?

A favourite talking point among ‘climate sceptics’ is the fact that even compared to the worst projected outcomes of anthropogenic (man-made) global warming, the planet has been hotter before – and yet managed to support a thriving biosphere. Talk of ‘saving the planet’ is, therefore, hyperbolic – the planet will be just fine, they say.

On the face of it, they’re right. It helps to remember that we’re living through an atypically cold period in the Earth’s history. In fact, we’re still in an ice age – the Quaternary Glaciation – that started 2.58 million years ago. Luckily our own era is a relatively warm interglacial period, but it’s still chilly compared to how things were before the start of the current ice age.

In a fascinating article for Palladium, Patrick Mellor describes the good old days:

“The Antarctic Ice Sheet covered only a small area around the pole, the rest of the continent supporting mixed forests of conifers and southern beeches. The coastlines of the continents were many miles further inland than today.

“In contrast to the usual apocalyptic narratives, the tropics were not scorched wastelands. They were covered with luxuriant rainforests containing up to 100 species of ape, including our own ancestors. Temperatures were up to 10℃ higher than today at the poles, but the tropics were not much hotter.”

So, given the bigger picture, is man-made global warming anything to worry about? The answer to that is yes, because as a species we’ve evolved in accordance with Earth’s current conditions. We’re not fit to live in the much warmer climate of the distant past. The few millennia in which we’ve become a civilisation of billions have exhibited a narrow range of climatic conditions. We know that life in general can adapt to massive shifts in temperature, but there’s no evidence that we can.

Furthermore, while there are precedents (and then some) for the degree to which human activity is pushing up carbon dioxide concentrations in the atmosphere, there is no precedent for the speed of the change:

“…our emissions are occurring over a period of centuries, rather than tens of millennia. Even the most extreme natural events would release only on the order of 1 gigaton per year, whereas in 2017, global CO2 emissions were about 41 gigatons.

“…our own maximum total impact is well within the limits of the largest natural events that have occurred in prehistory, but is happening much faster, and is therefore significant. Judging by these prehistorical analogues, by default we can expect a very large impact: a mass extinction, significant loss of coastal land, and large changes to global weather patterns.”

If we end up doing our worst, then the consequences for biodiversity will be devastating (they’re pretty disastrous as it is). A large proportion of the planet’s species will not be able to adapt to the scale and rapidity of disruption and will therefore go extinct.

Of course, life itself will survive – and, as with all mass extinctions, there will be a long, slow recovery in which surviving species evolve into new lifeforms to fill vacant ecological niches. But this will only happen over millions of years. On any timescale of human relevance, the planet we leave to our descendants will be a graveyard – a torn patchwork of wrecked ecosystems limping into posterity.

However, some value lies in comparisons to Earth’s deep past. Mellor argues that we should pay attention to eras, long before our own, in which very high levels of atmospheric carbon dioxide were reduced by natural processes. If we could somehow replicate them then perhaps we could geoengineer the climate to offset the impact of our greenhouse gas emissions.

These natural processes include unusually rampant plant growth, in which enough carbon dioxide is absorbed and retained to make a difference. Mellor believes that we could make this happen again through something called oceanic iron fertilisation – adding cheap micronutrients to the seas to encourage giant blooms of algae. It is estimated that each ton of iron additives could produce enough extra plankton growth to sequestrate 10,000 tons of carbon dioxide.

For reasons I’ve explained before, geoengineering in whatever form involves taking a huge risk with the only planet we’ve got. By far the safest way forward is to switch from filthy fossil fuels to clean energy and stop causing the problem in the first place. However, if we do need a plan B, then Patrick Mellor makes a good case for the least worst of the main geoengineering options.

In fact, we could apply the underlying principle right now by planting more trees. Recent research shows that reforestation is a more powerful means of fighting climate change than previously thought. Before messing about with the oceans we should repair the damage we’ve done on land.

Humankind has entered a new era, one in which we are both capable and conscious of altering the natural world on a global scale. With boots that big and footprints that heavy, we must tread carefully.

Though we are capable of revolutionary change, our efforts are more wisely devoted to ceasing what we know to be bad and restoring what we know to be good.

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Peter Franklin is Associate Editor of UnHerd. He was previously a policy advisor and speechwriter on environmental and social issues.

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