A recent study by a team of 10 researchers in the journal Nature Geoscience, recalculates the carbon budget for limiting the Earth’s warming to 1.5 degrees Celsius above temperatures seen at the end of the 19th century. The study suggests there is more time to combat global warming than was initially thought, and maybe even a chance to stay below the stringent targets first calculated after the Paris Agreement. The publication has caused turmoil in the scientific community and the general public, the most contentious question being; is their research correct?
How do climate scientists establish their prediction models? Previous studies have defined pre-industrial temperature measurements by using the period of 1861 to 1890, when the first accurate data was recorded. In 1870, there had already been about 0.2 degrees Celsius of warming, leaving us with only 0.4 degrees Celsius left to go. Further analysis also indicated that this target required carbon emission to fall to zero within seven years, which was widely seen as impossible.
The new study however relies on improved climate models and more recent data. It claims we can actually emit 200 gigatonnes of carbon (GtC) after 2015, which is almost three times more than the initially calculated 70 GtC. To obtain these numbers, the team of researchers took into account that even the most complex earth model systems tend to overestimate historical warming, but at the same time underestimate historical CO2 emissions. It was found that these two main discrepancies accumulate over time, and thus led to an underestimation of the carbon budget we are thought to have available. By resetting uncertainties, and starting from where we are today, a new, more optimistic perspective was achieved.
Naturally, the research is turning a lot of heads and climate scientists are trying to figure out why exactly there is such a discrepancy between these numbers and previous ones. It is important to remember that even the best models leave out slower feedback mechanisms, such as methane emissions from a melting Arctic, and that models will most likely continue to be modified over the next few decades. Because of this, keeping close tabs on publications by climate experts will become increasingly important.
The conclusions from the recent study can easily be misinterpreted as suggesting that there is now less urgency to put in place environmental measures. In fact, whether the findings are correct or not should not influence our course of action. We are already on track to exceed the 200 GtC limit despite coal use mitigation, because rising oil and gas use mean we are still emitting record levels of carbon dioxide. Rather suggesting that we can slow down environmental efforts, the team of researchers hope that their findings will inspire people to be ever more motivated in pursuing the goals set out in the Paris Agreement.
Not all hope is lost though, and there are still reasons to keep an optimistic outlook about the future of our planet. Two years ago, China passed the peak increase rate of their CO2 emissions, indicating its total carbon emissions will start falling before 2025, which is ahead of its official target date of 2030. Furthermore, recent drops in renewable energy costs are facilitating the move towards a global energy transition. Governments and individuals taking action to limit emissions is spurring progress in governance and technology.