By Lydia Messling
Last week, the World Meteorological Organisation (WMO) announced that there was around a 20% chance that one of the next five years will be at least 1.5 degrees warmer than pre-industrial levels. The earth’s average temperature is already over 1 degree warmer than pre-industrial levels, and continues to rise as more greenhouse gas emissions are released into the atmosphere. The WMO forecast is significant as, in November 2016, countries signed the Paris Agreement, which included a commitment to keep warming “to well below 2°C and pursue efforts to limit it to 1.5°C”.
The WMO’s finding is especially concerning as last year they issued a similar forecast which estimated the chance of exceeding 1.5 degrees in five years to be just 10%. This suggests that the world is still failing to tackle climate change with sufficient urgency and casts further doubt on the possibility of hitting the 1.5-degree target. The clear implication of this is that we must prepare for a highly unstable climate in a world where average temperatures are well above the 1.5- and 2-degree temperature targets.
One swallow does not a summer make
So does the latest WMO forecast mean we’ll miss the Paris Agreement’s 1.5-degree target? Whilst still a cause for concern, even if one of the next five years surpassed 1.5 degrees, we would not have breached the Paris Agreement’s target, because this is calculated as a 30-year moving average.
It’s a bit like measuring your running speed. The qualify time for the men’s marathon in the Tokyo Olympics is 2 hours, 11 minutes, and 30 seconds. That’s an average of about 5 minutes per mile. Just because you managed to run a sub-5-minute mile on your morning run does not necessarily mean that you are now ready to go for gold at the Olympics (no matter how much Strava kudos your friends give you). It could have been a fast mile for a number of reasons. Maybe it was downhill, the wind was behind you, or you were only ever running one single mile full pelt before collapsing. To think you could now run that 5-minute mile 25.219 more times, and keep that pace, might seem a bit of a stretch. Instead, in order to establish your long-term trend, you need to compare your averaged speed across a much longer distance, much closer to a marathon length, in order to fairly judge your marathon potential. One mile is not a fair judge.
The same is true here. Whilst there’s a 20% chance we might hit an annual average of 1.5 degrees warmer in the next 5 years, this is quite different to stating that we’ve crossed the threshold of the Paris Agreement, as this threshold is determined by a 30-year average. This is so that the effects of natural variability can be accounted for. For example, 2015 and 2016 were both affected by El Niño, which meant the underlying human-caused warming was amplified. Indeed, the WMO report says that there is only a small chance – 3% – that the next five-year average will exceed 1.5 degrees.
A worrying direction of travel
In 2020, the Arctic is likely to have warmed by more than twice as much as the global mean. There are also still impacts of climate change to be felt between now and 2024. In 2020, many parts of South America, southern Africa, and Australia are likely to be dryer than the recent past. Between now and 2024, high latitude regions and the Sahel are likely to be wetter. Sea-level pressure anomalies suggest that the northern North Atlantic region could have stronger westerly winds, resulting in western Europe experiencing more storms.
A single year that is 1.5 degrees warmer than pre-industrial levels is not enough to surpass the 1.5-degree threshold as described by the Paris Agreement, but it is an indicator that it is within reach. There is still a lot of climate change to be experienced between now and the Paris Agreement target of 1.5 degrees of warming – more than enough to motivate us in ensuring we do not exceed it. However, it remains unlikely that collectively we will act fast enough to reduce our emissions meet the target. At the moment, we are on track for qualifying for a much warmer world, with an unstable climate unlike anything experienced in human history.