You think man can destroy the planet? What intoxicating vanity.
Let me tell you about our planet.
Earth is four-and-a-half-billion-years-old. There’s been life on it for nearly that long, 3.8 billion years. Bacteria first; later the first multicellular life, then the first complex creatures in the sea, on the land.
Then finally the great sweeping ages of animals, the amphibians, the dinosaurs, at last the mammals, each one enduring millions on millions of years, great dynasties of creatures rising, flourishing, dying away — all this against a background of continuous and violent upheaval. Mountain ranges thrust up, eroded away, cometary impacts, volcano eruptions, oceans rising and falling, whole continents moving, an endless, constant, violent change, colliding, buckling to make mountains over millions of years.
Earth has survived everything in its time. It will certainly survive us. If all the nuclear weapons in the world went off at once and all the plants, all the animals died and the earth was sizzling hot for a hundred thousand years, life would survive, somewhere: under the soil, frozen in Arctic ice.
Sooner or later, when the planet was no longer inhospitable, life would spread again. The evolutionary process would begin again. It might take a few billion years for life to regain its present variety. Of course, it would be very different from what it is now, but the earth would survive our folly, only we would not. If the ozone layer gets thinner, ultraviolet radiation sears the earth, so what?
Ultraviolet radiation is good for life. It’s powerful energy. It promotes mutation, change. Many forms of life will thrive with more UV radiation. Many others will die out. Do you think this is the first time that’s happened?
Think about oxygen. Necessary for life now, but oxygen is actually a metabolic poison, a corrosive glass, like fluorine. When oxygen was first produced as a waste product by certain plant cells some three billion years ago, it created a crisis for all other life on earth. Those plants were polluting the environment, exhaling a lethal gas. Earth eventually had an atmosphere incompatible with life.
Nevertheless, life on earth took care of itself. In the thinking of the human being a hundred years is a long time. A hundred years ago we didn’t have cars, airplanes, computers or vaccines. It was a whole different world, but to the earth, a hundred years is nothing. A million years is nothing. This planet lives and breathes on a much vaster scale.
We can’t imagine its slow and powerful rhythms, and we haven’t got the humility to try. We’ve been residents here for the blink of an eye. If we’re gone tomorrow, the earth will not miss us.”
- Michael Crichton, Jurassic Park
This is wrong. There's a lot of nasty possible outcomes. Let's assume the Big Rip idea is off the table.
A nearby supernova could extinguish all life. Just from radiation... it might not even visibly change the earth much, from a distance, for a while.
A big asteroid, or even another planet, could hit. The one that wiped out the dinosaurs was fairly large, but there's no limit to the devastation potentially. Our planet could be shivered into billions, nay, trillions, of fragments. Or thrown out of it's orbit, and wander the interstellar night.
And all the while, the sun is burning.
If life is wiped out, there's just no time here for it to restart.
By the logic of the Drake Equation, if intelligent life can emerge, it should be everywhere. It isn't. We could be the only intelligence in that bubble of the universe accessible at light-speed; and nothing we have ever seen indicates that barrier can be broken.
We are the last, best hope for life,
800 million Carbon dioxide levels fall to the point at which C4 photosynthesis is no longer possible. Multicellular life dies out.
1 billion[b] The Sun’s luminosity has increased by 10 percent, causing Earth’s surface temperatures to reach an average of ~320 K (47°C, 116°F). The atmosphere will become a “moist greenhouse”, resulting in a runaway evaporation of the oceans. Pockets of water may still be present at the poles, allowing abodes for simple life.
1.3 billion Eukaryotic life dies out due to carbon dioxide starvation. Only prokaryotes remain.
1.5–1.6 billion The Sun’s increasing luminosity causes its circumstellar habitable zone to move outwards; as carbon dioxide increases in Mars's atmosphere, its surface temperature rises to levels akin to Earth during the ice age.
2.3 billion The Earth’s outer core freezes, if the inner core continues to grow at its current rate of 1 mm per year. Without its liquid outer core, the Earth’s magnetic field shuts down, and charged particles emanating from the Sun strip away the ozone layer, which protects the Earth from harmful ultraviolet rays.
2.8 billion Earth’s surface temperature, even at the poles, reaches an average of ~420 K (147°C, 296°F). At this point life, now reduced to unicellular colonies in isolated, scattered microenvironments such as high-altitude lakes or subsurface caves, will completely die out.[c]
3 billion Median point at which the Moon’s increasing distance from the Earth lessens its stabilising effect on the Earth’s axial tilt. As a consequence, Earth’s true polar wander becomes chaotic and extreme.
3.3 billion 1 percent chance that Mercury's orbit may become so elongated as to collide with Venus, sending the inner Solar System into chaos and potentially leading to a planetary collision with Earth.
3.5 billion Surface conditions on Earth are comparable to those on Venus today.
5.4 billion With the hydrogen supply exhausted at its core, the Sun leaves the main sequence and begins to evolve into a red giant.
7.5 billion Earth and Mars may become tidally locked with the expanding Sun.
7.9 billion The Sun reaches the tip of the red-giant branch of the Hertzsprung–Russell diagram, achieving its maximum radius of 256 times the present day value. In the process, Mercury, Venus and possibly Earth are destroyed.
During these times, it is possible that Saturn's moon Titan could achieve surface temperatures necessary to support life.
8 billion Sun becomes a carbon-oxygen white dwarf with about 54.05 percent its present mass.[d]
14.4 billion Sun becomes a black dwarf as its luminosity falls below three trillionths its current level, while its temperature falls to 2239 K, making it invisible to human eyes.