By Roberta Attanasio, IEAM Blog Editor
Over the last month, much has been said about 2014 being the hottest year on record. The first announcement came from the Japan Meteorological Agency during the first week of January. Later, a joint announcement by NASA and NOAA reinforced the finding: 2014 was the hottest year in more than 120 years of record keeping. The joint announcement underscored the significance of two major scientific branches of the US government reaching the same conclusion through separate data analyses. Gavin Schmidt, Director of NASA’s Goddard Institute of Space Studies, said: “This is the latest in a series of warm years, in a series of warm decades. While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases.”
“Long-term trend” is the buzzword here. The World Meteorological Organization (WMO) called 2014 the hottest year on record, as part of a continuing trend. However, it specified that 2014 was warmer than other recent years by only a few hundredths of a degree and, therefore, there is minimal difference between the three hottest years – 2005, 2010 and 2014. In contrast, the UK’s national weather service, the Met Office, announced that 2014 was one of the hottest years on record globally, but declined to call it the hottest year. Colin Morice, a climate monitoring scientist at the Met Office, said: “We can say with confidence that 2014 is one of ten warmest years in the series and that it adds to the set of near-record temperatures we have seen over the last two decades.” He added that uncertainties in the estimates of global temperature are larger than the differences between the warmest years, thus limiting what can be said about rankings of individual years.
Uncertainty is the impossibility to exactly describe an existing state. In a recent National Geographic article, Joel Achenbach pointed out: “Scientists rarely proclaim an absolute truth or absolute certainty. Uncertainty is inevitable at the frontiers of knowledge.” To the non-scientist, uncertainty is “not knowing,” but to scientists, it is “how well something is known.” Uncertainty is an inherent component of the scientific process—in most cases, science reduces uncertainty without eliminating it.
Climate science is observational; it does not rely on controlled laboratory experiments. It is based on projections made with sophisticated computer codes, modeling a large part of the system. In the name of transparency, climate scientists like to point out the level of uncertainty associated with their model projections. For example, an event is deemed “very likely” if it has a 90% chance of occurring. In other words, uncertainty means risk, and an understanding of this risk is necessary for its management and for decision-making.
The focus on risk plays a major role in guiding discourse on climate policy and can lead to effective solutions. The interest is not only on what is most likely to happen, but also on what might possibly happen.
Unfortunately, when risk is seen as “uncertain,” its role in terms of policy and solutions sometimes shifts—uncertainty then appears to justify inaction. For example, people who doubt climate change often use uncertainty to justify their position, and the statement given by the Met Office provides them with one more chance to point out disagreements between climate scientists.
But is there real disagreement between the reports from NASA, NOAA, WMO and the Met Office? They all agree on the “long-term trend” of increasing temperatures, and they all acknowledge that the differences between 2005, 2010 and 2014 are minimal. The data certainly shows that 2014 is one of the hottest years on record. More importantly though, the uncertainty about whether 2014 takes first prize should not detract from what we know: carbon dioxide levels keep following an upward trend, polar ice sheets and glaciers are melting, sea levels are rising, oceans are more acidic, and floods, heat waves and droughts are more frequent. Climate change is happening here and now due to human activities. We need to act soon. There is much we can do. Responding now will lower the risk of unpredictable and potentially irreversible events caused by climate change.