Just 30 years to save the planet
The IPCC now knows exactly how close we are to tipping into dangerous climate change, writes James Mitchell Crow.
The year isn’t quite over, but the forecasts are already in: 2013 will be another record-breaking year for carbon emissions. This year they will hit 9.7 gigatonnes – a 2.1% increase over the 2012 figure, which was itself a record at the time.
The data comes in a report released on 19 November by the Global Carbon Project, an international group of climate scientists that have been documenting our carbon emissions since 2001. The one glimmer of good news is that the growth in emissions does at least seem to be slowing. The latest 2.1% rise is significantly below the 2.7% average annual increase we have seen since 2003.
Even a skerrick of positive climate news is welcome. The Carbon Project report landed just a few weeks after an even more doom-laden climate document. Back in September, scientists and government representatives from around the globe gathered in Stockholm to sign off on the dense scientific tome that is the Intergovernmental Panel on Climate Change’s latest climate report.
Rarely in history has a scientific document come in for such scrutiny. Even before its release, media outlets from the UK’s tabloid Daily Mail to the Economist picked over leaked drafts searching for supposed clues that the IPCC’s last major report in 2007 had overestimated global warming. In early September, the Mail on Sunday – followed by The Australian and other news outlets – claimed the IPCC was about to revise down dramatically its estimates for the rate at which the world is heating.
Unfortunately the report contained no such welcome surprises. Global warming is real, its effects can already be seen and felt, and we are the cause. But tucked at the end was a contentious new strand of science that seemed to fly under the radar of most media. What the IPCC wanted to unveil – and what policymakers finally agreed to include – was the concept of a “carbon cap”, the total amount of carbon we can emit if we are to avoid greater than 2°C of global warming. The figure is significant. It is the internationally agreed threshold that, once passed, will make our planet far less hospitable. We can expect frequent extreme weather events such as floods, droughts, cyclones, heatwaves and bushfires; the potential loss of ecosystems such as tropical reefs; and the growing risk of tipping points that trigger dramatic acceleration in warming (see The new bad boy on the block).
In a single paragraph, the document sums up the daunting challenge: at our current rate of carbon emissions, in just three more decades we will have blown past “maximum carbon” and committed ourselves to dangerous climate change.
It is still within our means to determine the fate of our planet.
“This is the major new information and it is very, very important,” says David Karoly, a climate change researcher at the University of Melbourne. Since 2009, a slew of research has established a surprisingly simple fact, he says. Despite the complexities of the climate system, there is a clear linear relationship between the cumulative amount of carbon dioxide that humans release into the atmosphere and the temperature increase that results. In other words, “every ton of carbon emitted in the past, the present and in the future constitutes a commitment for climate change”, says Thomas Stocker, co-chair of the IPCC working group that authored the report.
So how much is left in our carbon budget? According to Stocker and his colleagues, 1,000 gigatonnes of carbon. But given emissions of methane from agricultural, man-made and natural sources, the amount of CO2 we can afford to release drops down to 800 gigatonnes. Of the 800 gigatonnes, the lion’s share of the budget is already gone. We had emitted 531 gigatonnes of carbon by the end of 2011. That leaves less than 300 gigatonnes, and – as the Global Carbon Project data shows – each year we help ourselves to another 10 gigatonnes or so. “This says that you have to fall to zero global emissions by 2040 if emissions continue at current rates, because 30 years and then you’ve blown the budget,” Karoly says.
How to divide the remaining budget fairly looks set to become a major discussion point. Developed nations such as Australia and the US have arguably already gobbled more than their fair share. “This carbon cap has direct implications for negotiations in the UN framework convention on climate change,” says Stocker.
Elsewhere the IPCC document dismisses the notion, popular in certain sections of the media, that climate models are wrong and that global warming is not as bad as we thought – a view based on the slowdown in the rate of global warming in the last decade. The summary points out that long-term models have in fact been remarkably accurate and the so-called “pause” is easily accounted for by natural factors including irregular El Nino events, the release of volcanic ash clouds and the finding that over the past decade, the deep oceans have acted as more of a heat sink than usual (see Better climate models show no end to warming).
Despite its generally gloomy outlook, there was a silver lining to the report. It is still within our means to determine the fate of our planet and choose between an innocuous one degree or so temperature rise by the end of the century, or a catastrophic climb of 3.7°C or more. The report lays out a scenario in which a rapid switch to alternative energy sees our carbon emissions peak by around 2030 and then fall to zero by 2070. Crucially, we would then need to suck some CO2 out of the atmosphere, perhaps by growing biofuels and putting the carbon emissions from burning them into geological storage. This approach would keep global warming safely below 2°C.
The critical issue is what our alternative energy source would be if we can’t release any carbon. An increasing number of climate scientists are stepping forward to press the case for nuclear power.
In their open letter “To Those Influencing Environmental Policy But Opposed to Nuclear Power”, leading climate scientists including James Hansen at Columbia University in New York and Ken Caldeira of the Carnegie Institution in California urge policymakers to reconsider nuclear as a viable low-carbon energy source.
“Nuclear energy is the only way that we can solve a problem of this magnitude,” says co-signatory Tom Wigley, a visiting research fellow at the University of Adelaide and former director of climate research at the University of East Anglia, UK. Wigley points to the new generation of nuclear power plant designs, which are dramatically cleaner and safer than plants such as Fukushima and even consume their own waste. “In the next 10 years, when things get a bit worse, people might wake up and realise that we have the answer.”
The IPCC explained
The Intergovernmental Panel on Climate Change may be the voice of climate science, but it is not a research agency: it gathers no raw data, and runs no computer models for predicting climate futures.
The job of IPCC chair Rajendra Pachauri and his team of scientists is to gather up all the research published by the climate science community at large, pooling it into an over arching report that summarises the current consensus in the scientific community on the Earth’s climate.
Established by the United Nations in 1988, the panel was set up to give governments around the world “a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts”.
Its task is divided between three working groups: group I, which published the 27 September report, looks at the science behind our warming atmosphere, rising oceans and melting glaciers, and forecasts future climate change; group II examines the impacts of these changes on people and the natural world; and group III considers mitigation options for curbing or offsetting greenhouse gas emissions.
In March and April 2014, working groups II and III will release their own reports. The concluding “synthesis report” should appear at the end of October 2014, completing the IPCC’s fifth assessment report on climate change.