Complex changes driven by greenhouse gas concentrations
Before the 18th century, when humans in the industrial west began to burn coal, oil and gas, our atmosphere typically contained about 280 parts per million (ppm) of carbon dioxide.
Those are the conditions on which civilization developed and to which life on Earth is adapted, sort of speaking.
An overwhelming 97% of scientists agree that climate change is being caused by human greenhouse gas emissions. There is no meaningful debate about the basic science of climate change.
Now, as the use of fossil fuels spreads through the world, the amount of carbon in the atmosphere is skyrocketing – we’re now well over 415 ppm of CO2 in the atmosphere.
But what does that actually mean?
Last year will go down in history as the year when the planet’s atmosphere broke a startling record by reaching the ~400 parts per million of carbon dioxide. The last time the planet’s air was so rich in CO2 was millions of years ago, back before early predecessors to humans were likely wielding stone tools; the world was a few degrees hotter back then, and melted ice put sea levels tens of meters higher.
So now we know that the increase of CO2 has happened in an utterly rapid pace, exponentially, and not at all sustainable.
We understand greenhouse gas as any gas that has the property of absorbing infrared radiation (net heat energy) emitted from Earth’s surface, and reradiating it back to Earth’s surface, thus contributing to the greenhouse effect. Carbon dioxide, methane and water vapour are the most important greenhouse gases.
By trapping heat from the sun, greenhouse gases have kept Earth’s climate habitable for humans and millions of other species. But those gases are now out of balance and threaten to change drastically which living things can survive on this planet—and where.
The roots of the greenhouse effect concept lie in the 19th century, when French mathematician Joseph Fourier calculated in 1824 that the Earth would be much colder if it had no atmosphere.
Nearly a century later, American climate scientist James E. Hansen testified to Congress that “The greenhouse effect has been detected and is changing our climate now.”
Today, climate change is the term scientists use to describe the complex shifts driven by greenhouse gas concentrations, that are now affecting our planet’s weather and climate systems, and its effects are far from being only environmental – they stretch to human health as respiratory diseases from smog and air pollution, increase of skin cancer cases, amongst others.
Extreme weather, food supply disruptions, and increased wildfires are other effects of climate change caused by GHG.
When we talk about global economy, virtually every sector, from manufacturing to agriculture to transportation to power production, contributes greenhouse gases to the atmosphere, so all of them must evolve away from fossil fuels if we are to avoid the worst effects of climate change.
But not all is lost!
The technologies for ramping down greenhouse gas emissions already exist, for the most part. They include swapping fossil fuels for renewable sources, boosting energy efficiency, and discouraging carbon emissions by putting a price on them.
The world technically has only one-fifth of its “carbon budget”—the total is 2.8 trillion metric tons remaining, in order to avoid warming the Earth more than 1.5 degrees Celsius.
The two goals outlined by the IPCC (Intergovernmental Panel on Climate Change) rely in some way on adopting methods of sucking CO2 from the sky. Those include planting trees, conserving existing forests and grasslands, capturing CO2 from power plants and factories and migrating from earth to ocean, exploring alternatives with seaweed and carbon sequestration.
“If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, CO2 will need to be reduced to at most 350 ppm,” Columbia University climate guru James Hansen has said.
We sailed past that target in about 1990, and it will take a gargantuan effort to turn back the clock.