Even limiting human-made global climate warming to 2°C above preindustrial temperatures would subject young people, future generations and nature to irreparable harm, leading scientists said on Tuesday. The team led by pioneering climate researcher Jim Hansen, now at Columbia University in New York, calls aiming for this internationally-recognised threshold ‘foolhardy’. In a paper published in PLOS ONE, they outline a case for aiming for 1°C that supports efforts to sue the US government for not doing enough.
“Governments are blatantly failing to do their job,” Jim told me. “They know that human-caused climate change is beginning and poses a huge risk to young people and future generations, and they understand that we must phase out fossil fuel emissions. Yet they go right ahead encouraging companies to go after every fossil fuel that can be found!”
As one of the first climate modellers, Jim has long warned about the greenhouse effect caused by the CO2 we emit from burning fossil fuels. On a sweltering June 23, 1988, he famously testified to the Energy and Natural Resources Committee of the US Senate on the dangers of global warming. “It’s time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here,” he told reporters at the time.
Yet Jim remains frustrated at the slow pace of action, and regularly voices it. In 2006 Mary Wood from the University of Oregon Law School saw one of his articles in the New York Review of Books and contacted him. Her work inspired the formation of a team of lawyers who are suing the US federal government, highlighting the principle that US citizens, young and old, have ‘equal protection of the laws’. “I agreed specifically to write a paper that would provide the scientific basis for legal actions against governments for not doing their job of protecting the rights of young people,” Jim recalled.
No time to waste
Then director of the NASA Goddard Institute for Space Studies, Jim mentioned the project to his colleague Pushker Kharecha, who eagerly joined him. And then, as the paper grew to span the many varied ways that climate change affects us, James progressively recruited many world-leading experts to help. The 18 authors range from economist and United Nations (UN) advisor Jeffrey Sachs, to biologist and lead author for the UN Intergovernmental Panel on Climate Change (IPCC) Camille Parmesan.
Together they used evidence from Earth’s history and measurements of the imbalance in energy entering and leaving Earth’s atmosphere to work out the safe level of global warming and a corresponding limit to how much fossil fuel we can burn. The historical data highlight threats from 2°C global warming, such as around six metres of eventual sea level rise.
But the major reasons there’s such a difference between 1°C and 2°C are ‘slow amplifying feedbacks’ that drive even more warming. These include reduced ice sheet area, changes in plant growth, for example forests appearing in currently sparse areas of northernmost Asia and North America, and increased amounts of nitrous oxide and methane in the air. Their effects are small if warming stays at around 1°C, but substantial if it reaches 2°C or more. “2°C global warming would have consequences that can be described as disastrous,” the researchers write.
The Earth has already warmed 0.8°C in the past 100 years, meaning the 1°C threshold is near. To stay below 1°C warming, Jim’s team recommend a target level of CO2 in the air of 350 parts per million (ppm). Before the world started to industrialise the level was 285 ppm, and in October 2013 it was 394 ppm. They find that if CO2 emissions were halted in 2015, CO2 would be back down to 350 ppm by the end of the century. “A 20 year delay in halting emissions has CO2 returning to 350 ppm at about 2300,” they write. “With a 40 year delay, CO2 does not return to 350 ppm until after 3000. These results show how difficult it is to get back to 350 ppm if emissions continue to grow for even a few decades.”
In a statement on Wednesday, Jim and Pushker admitted that phasing out fossil fuel emissions was a huge task. However they feel it’s technically possible with renewable energy and nuclear power. They say that these technologies would “readily outcompete fossil fuels in the marketplace if there were a fair, rising, and significant price on carbon emissions”. “When the world’s leading nations recognize the urgency of phasing out fossil fuel emissions, and realize that we are all in the same boat, it should be possible to agree on cooperative technology development and deployment, they write. “History, including World War II and the Apollo program, reveals how rapidly technology can be developed and deployed. Phase-out of most coal emissions and a halt of unconventional oil and gas use could be achieved rapidly. This would require agreement among leading nations not only to have common internal rising carbon fees, but also an agreement to cooperate in rapid technology development.”
Without that effort, they project a change in fortune between generations, “with young people and future generations inheriting a situation in which grave consequences are assured, practically out of their control, but not of their doing”. “The possibility of such intergenerational injustice is not remote – it is at our doorstep now,” they write. “We have a planetary climate crisis that requires urgent change to our energy and carbon pathway to avoid dangerous consequences for young people and other life on Earth. Our parents’ generation did not know that their energy use would harm future generations and other life on the planet. If we do not change our course, we can only pretend that we did not know.”
James Hansen, Pushker Kharecha, Makiko Sato, Valerie Masson-Delmotte, Frank Ackerman, David J. Beerling, Paul J. Hearty, Ove Hoegh-Guldberg, Shi-Ling Hsu, Camille Parmesan, Johan Rockstrom, Eelco J. Rohling, Jeffrey Sachs, Pete Smith, Konrad Steffen, Lise (2013). Assessing “Dangerous Climate Change”: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature PLOS ONE DOI: 10.1371/journal.pone.0081648