Even after reducing emissions, we still have to face “forced warming”

(ORDO NEWS) — Now few people doubt that man is changing the Earth’s climate. The big question is how quickly can we stop or even reverse this damage?

Part of the answer to this question lies in the concept of “planned warming”, also known as “pipeline warming”.

It refers to the future rise in global temperatures that will be caused by already emitted greenhouse gases. In other words, if the transition to clean energy happened overnight, how much warming would still occur?

The energy budget of the Earth is violated

Humans cause global warming when their activities release greenhouse gases that trap heat in the lower atmosphere, preventing it from escaping into space.

Before humans burned fossil fuels to run factories and vehicles and raised methane-emitting livestock in nearly every arable region, the Earth’s energy budget was roughly balanced. About the same amount of energy came in from the Sun as it went out.

Today, the rising concentration of carbon dioxide in the atmosphere is more than 50 percent higher than at the dawn of the industrial age, and it traps more and more energy.

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These carbon dioxide emissions, together with other greenhouse gases such as methane, and offset by some aspects of airborne pollution, trap energy equivalent to five Hiroshima-type atomic bombs per second.

As more energy enters than leaves, the Earth’s thermal energy increases, raising the temperature of the land, oceans, and air, as well as the melting of ice.

Warming in perspective

The consequences of changes in the energy balance of the Earth are not immediately apparent. Think about what happens when you turn a hot water faucet all the way on a cold winter’s day: The pipes are filled with cold water, so it takes time for the warm water to reach you – hence the term “pipe warming.” Warming is not yet felt, but it is already in the process.

There are three main reasons why the Earth’s climate is expected to continue warming after emissions cease.

First, the leading factors of global warming – carbon dioxide and methane – remain in the atmosphere for a long time: on average, about 10 years for methane and about 400 years for carbon dioxide, and some molecules persist up to millennia.

Therefore, shutting down emissions will not instantly reduce the amount of these heat trapping gases in the atmosphere.

Even after reducing emissions we still have to face forced warming 2

Second, some of this warming has been offset by anthropogenic emissions of another form of pollution: sulfate aerosols, tiny particles released when burning fossil fuels that reflect sunlight into space.

For the past century, this global dimming has masked the warming effect caused by greenhouse emissions. But these and other artificial aerosols also harm human health and the biosphere.

Removal of these and short-lived greenhouse gases will result in additional warming of a few tenths of a degree for about a decade before a new equilibrium occurs.

Finally, the Earth’s climate takes time to adjust to any changes in the energy balance. About two-thirds of the Earth’s surface is water, sometimes very deep water, which slowly absorbs excess carbon and heat.

Even after reducing emissions we still have to face forced warming 3

To date, more than 91 percent of the heat added by human activity and about a quarter of the excess carbon has ended up in the oceans.

While land dwellers may be grateful for this buffer, the extra heat contributes to sea level rise through thermal expansion as well as marine heatwaves, while the extra carbon makes the ocean more hostile to many armored organisms, which can disrupt the ocean food chain.

The temperature of the Earth’s surface, driven by an imbalance of radiant energy in the upper atmosphere and modulated by the enormous thermal inertia of the oceans, is still playing catch-up with its largest control knob, carbon dioxide concentration.

How much warming?

So what kind of warming awaits us? There is no single answer.

The world has already warmed by more than 1.1 degrees Celsius compared to pre-industrial levels. In 2015, countries around the world agreed to try to keep the global average from rising more than 1.5°C to limit the damage, but the world has been slow to respond.

It is rather difficult to determine the volume of the forthcoming warming. A number of recent studies use climate models to estimate future warming. A study of 18 earth system models found that when emissions stop, some continue to warm for decades to hundreds of years, while others cool rapidly.

Another study published in June 2022 found that there is a 42 percent chance that the world will already reach 1.5 degrees.

The amount of warming matters because the dangerous effects of global warming don’t just increase in proportion to global temperature; they tend to increase exponentially, especially for food production at risk from heat, drought and storms.

In addition, the Earth has tipping points that can cause irreversible changes in fragile parts of the earth system, such as glaciers or ecosystems. We don’t always know right away when the planet will be at a tipping point, because these changes are often slow to manifest. These and other climate-sensitive systems underlie the precautionary principle of limiting warming to 2°C, preferably 1.5°C.

The crux of the climate problem inherent in this idea of ​​sustainable warming is that there is a long delay between changes in human behavior and changes in climate.

While there is still some debate about the exact amount of recorded warming, the evidence shows that the safest path forward is an urgent transition to a carbon-free, more equitable economy that produces far fewer greenhouse gas emissions

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