Stop the doom. We failed to prevent climate change – but we will decide how bad it'll get.

Are we finally seeing meaningful action on climate? If you’re an optimist, you might be encouraged by the climate provisions of the Inflation Reduction Act, signed into law last year by President Joe Biden, which are starting to bear fruit. 

And among other developments, California – the world’s fifth largest economy – is now flexing its climate action muscle, bringing a lawsuit against carbon polluters for the damage they have caused.

But these developments are long overdue. More than three decades ago, the nations of the world entered into an agreement to prevent “dangerous human interference” with the climate. Thanks to this past summer, we can see that the danger's already here and we know what it looks like. 

It looks like the Hawaiian paradise of Maui set ablaze in a deadly inferno born of extreme drought. It looks like the orange tinge of my home city of Philadelphia shrouded in choking Canadian wildfire smoke. Or the faces of grief-stricken families in nearby Bucks County who lost loved ones to a “wall of water” from an epic flash flood. It looks like the flooded streets and homes of quintessential New England towns. And the scalded feet of toddlers in Phoenix who made the mistake of walking out onto toaster oven-hot pavement. 

Dangerous climate change is a shape-shifting beast, but we've just seen it in all its forms. 

The few remaining climate change dismissives respond with their usual refrain “that’s just weather.” But there is a larger context here, the context provided by Earth’s longer-time climate history, that tells us otherwise. An array of paleoclimate evidence – from ice cores, tree rings and corals to ocean sediments, stalactites and stalagmites – indicates that we might well have just experienced the warmest days of the warmest month in at least 100,000 years. Hardly just some fluke roll of the weather dice. 

That realization might seem daunting and disquieting, because it speaks to the fragility of this moment. We are, after all, rapidly exiting the range of climate conditions that prevailed during the roughly 6,000-year period in which human civilization arose. Does this mean that our civilization is now threatened? That it’s too late to act? Are we – in essence – doomed?

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Both climate deniers and 'doomers' can lead to inaction

You might think so while doomscrolling on social media, where we’re now bombarded with selective factoids and graphics leading us to believe that Earth’s climate is spinning out of control, that runaway warming is propelling us past a tipping point, plunging us down a planetary death spiral.

Might as well just bid goodbye to your loved ones now.

We’re told by climate “doomers” that scientists who insist there’s still time to act are lying to the public, hiding the inevitability of our collective demise. These accusations mimic those of years and decades past from climate dismissives. Both doom and denial can lead us down a path of disengagement, which is so convenient to fossil fuel interests that profit from climate inaction.

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The reality is that global temperatures are almost where models decades ago predicted they would be at this point given ongoing fossil fuel burning. No runaway warming, but steady heating that will continue as long as we emit carbon pollution. The truth is bad enough – it’s reason enough for dramatic action.

And Earth’s climate history reveals the truth, offering not just thousands but billions of years' worth of lessons.

Let’s begin 4 billion years ago, when life emerged from the primordial ooze. The sun then was roughly 30% dimmer than today. Calculations indicate that, all else being equal, Earth should have been a frozen, lifeless planet. Yet we know it wasn’t. Life abounded. 

The solution to this paradox, first offered by scientist Carl Sagan, was that the planet-warming greenhouse effect must have been even stronger then. Moreover, as the sun gradually grew brighter over the ensuing billions of years, Earth’s greenhouse effect grew weaker.

Earth appears to have a natural “thermostat” that keeps the planet within habitable bounds and life itself – including the global carbon cycle that helps regulate the concentration of carbon dioxide, a critical greenhouse gas – plays a critical role. This is the “Gaia hypothesis,” named after the Greek Earth goddess, first formulated by scientists James Lovelock and Lynn Margulis in the early 1970s. There is now substantial evidence to back it up.

So we can relax then? The natural stabilizing mechanisms of Earth’s climate will bail us out?

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Not necessarily. For there is also evidence for the opposing "Medea hypothesis" proposed by paleontologist Peter Ward, named after the mythological figure who killed her own children. There are amplifying mechanisms that can, at least at times, cause Earth’s climate to spin out of control.

Consider the "Great Oxidation Event" roughly 2 billion years ago when a dramatic rise in oxygen-producing bacteria rapidly scavenged much of the potent greenhouse gas methane, leading to a vicious cycle of cooling, ice buildup and more cooling. Our planet appears to have become entirely encased in a shell of ice – "Snowball Earth.” Life nearly died off, surviving only by seeking refuge in warm environments such as hydrothermal vents in the deep ocean.

Paleoclimate history reveals these dueling narratives of fragility and resilience. Yes, we have failed to prevent dangerous climate change. It is here. But it’s up to us as to how bad it will get.

Today we are generating carbon dioxide more than 10 times faster than in any of these past episodes. If we do not dramatically reduce carbon emissions, the paleoclimate record tells us we will, in a matter of decades, exceed levels of warmth not seen in millions of years. It is the unprecedented rate of change today that poses a monumental challenge to life on this planet.

A window of opportunity still remains for averting a catastrophic warming of the planet by 3 degrees Fahrenheit, where we’ll see far worse consequences. But that window is closing, and we’re not yet making enough progress.

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We must not give in to despair. The antidote to doom is doing.

We are seeing meaningful progress. And we should be especially inspired by youth climate activists, the same ones who marched in New York City recently to demand action.

Lest we think this is all talk and performance, youth climate activists won a landmark court case last month in Montana that could set a precedent for future cases. The court found that the state had violated their constitutional right to a “clean and healthful environment” by promoting fossil fuels.

It’s a major victory for climate advocates, but we cannot leave action to the youngsters. Those of us in a position to vote and influence policy must do so now while there’s still time to preserve our fragile moment.

Michael E. Mann is a Presidential Distinguished Professor and director of the Penn Center for Science, Sustainability & the Media at the University of Pennsylvania. He's the author of the new book "Our Fragile Moment: How Lessons from Earth's Past Can Help Us Survive the Climate Crisis."