How Long Do Scientists Think Life On Earth Has Left?

We’ve got about five billion years ’til the Sun dies, which certainly wouldn’t spell good news for planet Earth.

But researchers have long thought we’d be gone way before that happens. The Sun is always expanding, and will probably swallow our little planet up like a whale does plankton one day. (At least, that’s according to some theoretical models).

Not only that, but it’s getting increasingly luminous and producing more and more energy.

Now, a paper published in the journal JGR Atmospheres has attempted to put a finer point on when we might all be (literally) cooked.

“The ultimate life span of Earth’s biosphere is limited due to the steady brightening of the sun as it progresses in age,” they wrote, but caveated it “could survive for much longer than indicated in most studies”.

The paper said that as the Sun ages, “Earth’s long-term carbon cycle may respond by drawing carbon dioxide [CO2] out of the atmosphere and into carbonate rocks, thereby reducing the greenhouse effect and offsetting the increased sunlight”.

Previous studies have argued that this would make CO2 levels too low to sustain life on Earth – it’s vital for supporting oxygen-giving trees, for instance. This idea led some scientists to estimate the end of plant life on our planet at about 100 million years into the future.

In this study, however, scientists used 29 different models to work out what might happen to Earth under different conditions.

They modelled two extremes: one in which the world was too hot for life but had enough CO2, and another in which the temperature was more livable but CO2 levels were shot. They also looked at the range of conditions between these.

And the study authors input data about various plants, like succulents and orchids, which can survive on very little carbon dioxide.

“We show that Earth’s biosphere could survive for much longer than indicated in most studies, noting that some photosynthetic life on Earth can thrive at very low carbon dioxide levels,” the paper reads.

Their models suggested Earth’s vegetative biosphere could survive up to roughly 1.8 billion years from now, “about the same time that Earth would lose its oceans to space”.

Speaking to Live Science, Robert Graham, a planetary science researcher at the University of Chicago (who wasn’t part of the research), said: “The Earth has stayed pretty hospitable in terms of surface temperature for most of the last 4 billion years because it has a built-in thermostat.”

That refers to the CO2-pulling strategy we mentioned earlier – in hotter weather, the world pulls carbon dioxide out of the environment and stores it underground. Therefore, less heat from the sun gets trapped, and the planet cools again (if at the previously-presumed expense of photosynthesis, and as a result, life on Earth).

But the researchers of this study “have used a sophisticated 3D climate model to show that Earth’s climate may remain hospitable to plant life significantly longer into the future than predicted,” Graham said.

“It’s an advance over previous work and suggests that complex biospheres like that of Earth are more resilient to environmental change from stellar brightening than previously suggested.”