The full story on climate change requires the long view

The full story on climate change requires the long view
The pie charts show relative contributions to global warming divided into regions of the world. The enlargements represent the growth of overall cumulative global radiative forcing. CRF is cumulative radiative forcing. RCP is representative concentration pathway, or a modeled emissions scenario based on prior inputs. RCP 2.6 is roughly what was agreed upon during the 2015 Intercontinental Panel on Climate Change, the "Paris Agreement," in which nations collectively agreed to limit global warming to 1.5 degrees Celsius this century. RCP 8.5 is business as usual, with continued increasing emissions. Credit: A.R. Ravishankara/Colorado State University

The science is clear that human activities over the last century have contributed to greenhouse-like warming of the Earth's surface. Much of the global conversation around climate change fixates on what individual countries or regions are contributing to the problem, and what they will do (or not do) to reverse the tide.

But Colorado State University's A.R. Ravishankara, University Distinguished Professor who holds joint appointments in the departments of chemistry and atmospheric science, says the full picture is longer and more complex than meets the eye. It involves a legacy of past actions, as well as irreversible commitments for the future.

Ravishankara and co-author Daniel Murphy of the National Oceanic and Atmospheric Administration offer a new calculation that provides the long view of what nine different world regions have contributed to since 1900. They also show how that breakdown will likely look by 2100 under various emission scenarios. Their study is in Proceedings of the National Academy of Sciences, Dec. 17.

They call their calculation "cumulative radiative forcing" because it integrates the ebb and flow of factors throughout the past century, rather than just a snapshot of what it is today. "Radiative forcing" is a metric that measures the sun's energy that is retained by Earth. Global warming is the result of positive radiative forcing, or more energy being retained by Earth than escaping back into space.

Their study also underscores the insidious two-sided role of particulate matter pollution in the atmosphere, the result of burning fossil fuels, wildfires, and other human activities that have spewed pollution and dust into the atmosphere over many decades. Such aerosols are short-lived in the atmosphere, but they have a net cooling effect due to their interaction with sunlight and clouds. While carbon dioxide and other greenhouse gases linger in the atmosphere and continue contributing to warming for many years, aerosols dissipate, along with their net cooling effects, more quickly. In total, the presence of aerosols has masked some of the effects of global warming.

In their analysis, the researchers found that, for example, between 1910 and 2017, China, Europe and North America each had periods of nearly no net contributions to warming. These periods were characterized by rapid industrialization and growth of GDP, when fossil fuel emissions increased but few air quality controls were enforced. The study further shows that each region's contribution to due to carbon dioxide (and other greenhouse gases) emissions from 2018 to 2100 will be larger than the total warming contributed during the last century.

"To date, China has contributed very little," Ravishankara said. "China has essentially paid for their carbon dioxide emissions through bad air quality."

But as China implements clean air standards moving forward, and the nation's emissions increase at a slower rate, its share of contributions to climate change will increase, according to the study. North America is the largest contributor now and will remain so even in 2100.

The two-sided coin of aerosols—short-lived cooling, but harmful to human health—is starkly illustrated in a separate study authored by CSU postdoctoral researcher Liji David, Ravishankara and other colleagues, to be published online in GeoHealth. The researchers estimate that more than 1 million per year in India are due to exposure to "ambient particulate matter—air pollution in the form of breathable particles like sulfate aerosols, dust and soot. In India, residential energy use—biomass burning in homes for heating and cooking—is the dominant contributor to this premature mortality rate.

Of the estimated 1.1 million premature deaths in 2012 from small particulate matter in India, about 60 percent were due to anthropogenic pollutants emitted within the region, according to the study.

Yet to date, India's contribution to climate change has been minimal as shown by Murphy and Ravishankara in PNAS, as it will be even by 2100, compared with other nations. As India implements clean air policies and works to reduce premature deaths from air pollution, its role in climate change may increase due to the aerosols playing less of a role in offsetting climate change, but human health will improve.

Ravishankara stresses that people should look at effects of emissions holistically. Future climate scenarios must take into account all warming contributions to date, and the effects of those contributions moving forward. Emissions reductions would not only help climate, but also human health, he says. Aggressively reduced and other emissions, for the sake of the planet and for the sake of , are the only viable options.

"We need to ask not only what is our commitment going forward but also what is our legacy?" Ravishankara said.


Explore further

Particulate pollution's impact varies greatly depending on where it originated

More information: D. M. Murphy el al., "Trends and patterns in the contributions to cumulative radiative forcing from different regions of the world," PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1813951115
Citation: The full story on climate change requires the long view (2018, December 17) retrieved 25 April 2019 from https://phys.org/news/2018-12-full-story-climate-requires-view.html
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Dec 17, 2018
Peak oil is coming. Given that the hockey stick population growth chart mirrors the hockey stick oil production graph over the last 150 years, the two most important policies right now to get a handle on sustainability and avoid calamity are:

1) global solar panels on all rooftops

2) global two child max

The global warmists work for the billionaires who have no vision for your future except to control and reduce demand for fossil fuels, so they can keep their money machines printing as long as possible.

Dec 17, 2018
Production of solar panels is a very carbon costly.

Two Child max, thank you Mr Orwell

Mind police might be good too, so the government can correct abhorrent thoughts.

Dec 17, 2018
Yes, what better way to use the fossil fuel carbon boom than to create a sustainable head start with a universal energy source that has a good EROEI. Pick another if you have a better one. Starting after the shortages start is too late, at least for a few billion people.

This rock only has only so much room; family planning is preferable to a future die-off, or a billionaire devised thermonuclear war to cull the herd.

You have Orwell mixed up. We need information transparency and accountability of our failed leadership right now, not more Orwell. We already sort of do, in a way. The ass-clowns just don't know it yet. Ours is the first generation in history whose whole digital lives are being recorded, archived and collated. Tomorrow's technology will continue to exceed what is being done today with google and Facebook aggregator files, credit reports, background checks, etc. Fitting I suppose for the fiddlers.

Dec 17, 2018
Still can't run your models from 1900 to today and get results that are close to today's climate, can you?

Dec 17, 2018
Two-child maximum is already the law of the Communist Party in China - while here in the western world, the taxpayer-funded abortion clinics (that Socialists hold so dear) are murdering innocent foetuses/live-birth babies without remorse.
And, in the UK, innocent young children are taught by their teachers (and some parents) that boys can also have menstrual periods. Of course, those are actually girls whose convoluted minds have caused such a cognitive dissonance from which they may never recover. But the State is colluding with their insanity.
It is sad the way the humans are heading - so that it isn't really any wonder that the Earth is "so fit to be tied" that earthquakes are happening so much more frequently, and there is a possibility that ALL or most land masses will sink back into the oceans from whence they came billions of years ago. Thus, mankind has fuucked up again and they won't stop until the Earth is ruined and the lavas flow to inundate where humans once trod.

Dec 17, 2018
One long view, often forgotten in the climate change conversation, is that over 100 million humans have been killed by air pollution in the last few decades. More than in all of the world wars together.

We talk about whether the weather is changing, but meanwhile over 20,000 humans died today from simply breathing bad air. It's a very large elephant in the room.

The health care and liability costs from burning fuels exceeds hundreds of trillions of dollars worldwide. And that's nothing to do with CO2...

"Up to 1/3 of deaths from stroke, lung cancer and heart disease are due to air pollution...7 million deaths annually." https://www.who.i...d-health

Dec 18, 2018
This study is another brick in the Wall of Shame being erected around the disappearing middle class. Because environmental collapse and the death of humanity, why it's on their heads don't you know? Too much high living thanks to the miraculous uses of crude oil. But just wait until the $4/gallon gas tax becomes reality.

Meanwhile, 1900 is not the "long view." The real "long view" suggests it's been much warmer than now within the past 20,000 years, and probably about as warm as now within the past 2,200 years, yet no extinctions, no globe-killing drought, etc. What is up with that, ye intrepid modelers?


Dec 18, 2018
WOW! If only the dinosaurs had planned ahead.......................... they wasted 200 million years to solve the problem and what did they get for it....extinction. Maybe that guy that wants solar panels on every roof and a two child limit would be happy.

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