Researchers argue that reducing greenhouse gas emissions is not enough to combat climate change

A recent research published in Oxford Open Climate Change suggests that lowering greenhouse gas emissions won't be the only tactic mankind takes to combat climate change. This is the result of a study conducted by researcher James Hansen using climatic data.

Since the 1800s, scientists have been aware that both natural and man-made increases in the concentration of greenhouse gases cause the Earth's surface to warm. These gases absorb infrared light. One of the first scientists to investigate global warming, Roger Revelle, claimed in 1965 that industrialization entailed humans engaging in a "vast geophysical experiment" since burning fossil fuels released carbon dioxide (CO2) into the atmosphere. Currently, CO2 levels are higher than they have been in millions of years.

Climate responsiveness

The amount that the global temperature will climb for a given increase in CO2 is a long-standing question. According to a 1979 research published by the US National Academy of Sciences, global warming of 1.5 to 4.5°C would probably result from doubling atmospheric CO2 when ice sheets were frozen. This was a wide range, and there was also doubt regarding the contribution of Earth's enormous ocean to the warming delay.

Based on updated paleoclimate data, this new study reassesses climate sensitivity and concludes that it is more sensitive than previously thought. Their highest estimate of 4.8°C global warming with doubled CO2 is far higher than the UN Intergovernmental Panel on Climate Change's best estimate of 3°C.

Airborne Parts

The scientists also come to the conclusion that the cooling impact of aerosols—fine airborne particles produced by humans—has largely countered the predicted warming caused by greenhouse gases during the previous century. Due to worldwide limitations on ship-related aerosol emissions and decreased air pollution in China, the quantity of aerosols has decreased since 2010. Since particle air pollution kills several million people annually and negatively impacts the health of many more, the reduction of aerosols is favorable for human health.

Aerosol cooling had concealed greenhouse gas warming, but aerosol decline is now starting to reveal it. The authors have referred to the aerosol cooling for a long time as a "Faustian bargain" since greater warming is the price that must be paid until air pollution is finally reduced by humans.

According to this new research, global warming will accelerate after 2010 and surpass natural climatic variability. In the decades that follow 2010, it is expected that the 0.18°C per decade global warming pace from 1970 to 2010 would rise to at least 0.27°C per decade. Consequently, we will surpass the 1.5°C global warming threshold this decade and the 2°C threshold in the next two decades.


Hansen summarizes his viewpoint—which is informed by decades of experience attempting to influence government policies—in the concluding section. First, he thinks that in order to accomplish a quick phasedown of CO2 emissions, contemporary nuclear power must be supported in addition to renewable energy, and a growing domestic carbon charge with a border tariff on items from countries without a carbon price.

Secondly, he contends that poor countries need assistance from the West, which is mostly to blame for climate change, in order to attain energy pathways that are compatible with a favorable environment for all.

Third, Hansen contends that despite these efforts, global warming will still have harmful effects and that we should continue researching and developing short-term, deliberate measures to correct the massive energy imbalance that now exists on Earth.

Ten years ago, Hansen reported that there was a 0.6 W/m2 (watts per square meter) energy imbalance on Earth. Incoming energy (solar radiation received) exceeded outgoing energy (heat radiation to space) by a significant amount. This surplus, the direct source of global warming, is the same as 400,000 Hiroshima atomic bombs detonated every day, with the majority of the energy released into the ocean. Now, the imbalance has risen to around 1.2 W/m2, primarily due to decreased aerosols.

Later this century, this massive imbalance is anticipated to shut down overturning ocean circulations and create high, fast rising sea levels. It is also the primary source of accelerated global warming and increasing melting of polar ice.

The study makes the case that taking such action is necessary to prevent the larger geotransformation that would result from doing nothing. Possible interventions include spraying salty ocean water by unmanned sailboats in areas vulnerable to cloud seeding, and injecting aerosols into the stratosphere (for which volcanoes offer pertinent, although insufficient, test cases).

In western democracies, particularly in the US, there is an underlying issue that Hansen proposes young people concentrate on: "The ideal of one person/one vote has been replaced by one dollar/one vote," he asserted. "Political influence may be bought by certain financial interests, such as the chemical, food, timber, and fossil fuel industries. It is understandable why the climate is out of control, why environmental toxicity is eradicating pollinators and other insects, why forests are being mishandled, and why agriculture is being developed for profit rather than for human nourishment and welfare."

"We live on a planet with a climate characterized by delayed response, which is a recipe for intergenerational injustice," Hansen said. "Young people need to understand this situation and the actions needed to assure a bright future for themselves and their children."