Temperatures in north america from 26.12.17-2.1.18: extreme cold on one side, extreme warm on the other. Image: nasa earth observatory
Eth scientists say the weather-is-not-equal-to-climate paradigm no longer applies
How climate differs from weather? Climate is the term used to describe long-term trends, while weather is everything that happens in the short term under local conditions, although there can be some gross variability here. This sometimes leads to people like donald trump and cons like to point to cold days in the summer or other variability to demonstrate that climate warming is just a phantom. On the other hand, extremes and anomalies are seen as signs of climate change.
That the past decade has been the warmest on record, 1.1 degrees warmer than the pre-industrial era and 0.19 warmer than the 2000s confirms climate warming. In addition, one could ask whether it was not already earlier than that in the 19th century. It is hypothesized that the anthropocene that began in the nineteenth century had a marked effect on the climate, for example during the little ice age, when epidemics such as the black plague depopulated swaths of land around the world, and in the americas almost the entire population was carried off, leading to a drop in temperature from the 15. Until the 17. (the anthropocene begins with the conquest of the americas).
A report by climate scientist professor dr. Reto knutti’s team, led by eth, concluded after analyzing temperature data and climate models in their study published in nature climate change that the old distinction between weather and climate no longer applies because man-made climate warming can also be detected in daily weather data when surface temperature or humidity and global spatial patterns are taken into account. So even if there is a record cold, as occurred in utah last october of -37 degrees, but it has been correspondingly warmer in other regions, the local deviation is compensated for when a global perspective is taken, and the long-term trend is maintained.
Climate signal in weather data
Scientists talk about the climate signal that can be detected in daily weather data. To this end, they had developed statistical learning methods to combine simulations with climate models and data from measuring stations. With these statistical learning methods, the combination of temperatures and the relationship between expected warming and variability can be used to create the "fingerprint" of climate change – and this in the global quantity data for every single day since 2012.
The importance of the global perspective is confirmed by the comparison of local and global daily average temperatures in the period from 1951 to 1980 with the period from 2009 to 2018 then the distribution curves of the local average temperatures, which show a strong variability, overlap to a good extent, while the statistically determined average values of the global average temperatures show practically no overlap – and thus make the anthropogenic climate warming clear.
The scientists hope that their method will also enable them to make better predictions of extreme weather events against the background of climate warming. "With this one should", according to reto knutti, "in the future, it should also be possible to identify man-made patterns and trends in other more complicated measurement samples, such as precipitation, that are difficult to detect with traditional statistics."