No quick fix in fight against global warming — new study

Slashing greenhouse gas emissions probably won’t yield obvious results until mid-century, researchers have said, cautioning that humanity must manage its expectations in the fight against global warming.

Even under optimistic scenarios in which carbon pollution falls sharply, climate change will continue for decades, they reported on Tuesday in the journal Nature Communications.

“We need to be patient,” said lead author Bjorn Samset, a scientist at the Centre for International Climate Research in Oslo, Norway. “All reductions in warming emissions will lead to less heat being absorbed,” he said. “But for temperature — which is what we care about — it will take decades before we will be able to measure the effect.”

Two factors will make it difficult to feel and measure a drop in Earth’s surface temperature, if and when that happens.

LINGERS FOR CENTURIES

In the past half-century, human activity loaded the atmosphere with more than 1-trillion tonnes of planet-warming carbon dioxide (CO2), a gas that lingers for centuries.

“Human-induced climate change can be compared with an ocean tanker at high speed in big waves,” said Samset. “You can put the engine in reverse, but it will take some time before you start noticing that the ship is moving more slowly.”

The second factor was natural variability. In the past halfcentury, the planet warmed 0.2°C every decade, due mainly to the burning of fossil fuels.

“But from one year to the next, there are also large variations on a similar scale,” said Samset, comparing the variations to waves rocking a ship back and forth.

In their study, Samset and colleagues projected the effect of reducing the two main greenhouse gases — CO² and methane — as well as soot, sometimes called “black carbon”.

On a 100-year timescale, methane — with more “warming potential” but less long-lasting — is about 28 times more potent than CO². Its main man-made sources are livestock, agriculture and leaks from the natural gas industry.

Produced mostly by burning fossil fuels, CO² accounts for more than three-quarters of global warming.

Even with rapid cuts in these gases, it will be nearly impossible to detect a clear impact on global warming before 2035, the researchers said.

In a more realistic scenario, “these efforts could all be visible by mid-century, but not before”, the study concluded.

Reducing soot was found to have a negligible effect.

Scientists not involved in the research said it served as a reminder of what humanity is up against.

“The study reinforces our understanding that climate change is a long-term problem that will not simply disappear if all human-related emissions stopped tomorrow,” said Grant Allen, a professor of atmospheric physics at the University of Manchester.

“There is no quick fix.”

‘UNNECESSARILY GLOOMY’

For Andrew Watson, a Royal Society research professor at the University of Exeter, bending the curve of global warming “is like turning a supertanker”.

“We have spent many decades steering it in the wrong direction, and it will take decades for the results of climate mitigation to be obvious.”

But Piers Forster, a climate change professor at the University of Leeds, said the findings were “unnecessarily gloomy”.

Research has shown that with serious effort, society can have a “discernible cooling effect on Earth’s temperature over the next 15-20 years,” he said.

CLIMATE CHANGE ... WILL NOT SIMPLY DISAPPEAR IF ALL HUMAN-RELATED EMISSIONS STOPPED TOMORROW