Climate researchers can now detect the fingerprint of global warming in daily weather observations at the global scale.
In October 2019, weather researchers in Utah measured the lowest temperature ever recorded in the month of October in the US (excluding Alaska): -37.1°C (-34.78°F). The previous low-temperature record for October was -35°C (-31°F), and people wondered what had happened to climate change.
Until now, climate researchers have said that climate is not the same thing as weather. Climate is what we expect in the long term, whereas weather is what we get in the short term. Since local weather conditions are highly variable, it can be very cold in one location for a short time despite long-term global warming. In short, the variability of local weather masks long-term trends in global climate.
North American surface temperatures for December 26, 2017–January 2, 2018: Even if it is extremely cold in a region, this does not mean that climate change has stopped. (Credit: NASA Earth Observatory)
Now, however, a group led by Reto Knutti, a professor in the environmental systems sciences department at ETH Zurich, has conducted a new analysis of temperature measurements and models. The scientists concluded that the weather-is-not-climate paradigm is no longer applicable in that form.
According to the researchers, they can actually discern the climate signal—that is, the long-term warming trend—in daily weather data, such as surface air temperature and humidity, provided that global spatial patterns are taken into account.
In plain English, this means that—despite global warming—there may well be a record low temperature in October in the US. If it is simultaneously warmer than average in other regions, however, this deviation is almost completely eliminated.
Get The Latest From InnerSelf
“Uncovering the climate change signal in daily weather conditions calls for a global perspective, not a regional one,” says lead author Sebastian Sippel, a postdoc working in Knutti’s research group.
Sippel and his colleagues used statistical learning techniques to combine simulations with climate models and data from measuring stations. Statistical learning techniques can extract a “fingerprint” of climate change from the combination of temperatures of various regions and the ratio of expected warming and variability. By systematically evaluating the model simulations, they can identify the climate fingerprint in the global measurement data on any single day since spring 2012.
A comparison of the variability of local and global daily mean temperatures shows why the global perspective is important. Whereas locally measured daily mean temperatures can fluctuate widely (even after the seasonal cycle is removed), global daily mean values show a very narrow range.
Distribution of daily mean values locally (left) and globally (right). Global daily mean values show the trend towards warming. (Credit: Sippel et al./Nature Climate Change)
If researchers compare the distribution of global daily mean values from 1951 to 1980 with those from 2009 to 2018, the two distributions (bell curves) barely overlap. Therefore, the climate signal is prominent in the global values but obscured in the local values, since the distribution of daily mean values overlaps quite considerably in the two periods.
The findings could have broad implications for climate science. “Weather at the global level carries important information about climate,” says Knutti. “This information could, for example, be used for further studies that quantify changes in the probability of extreme weather events, such as regional cold spells. These studies are based on model calculations, and our approach could then provide a global context of the climate change fingerprint in observations made during regional cold spells of this kind. This gives rise to new opportunities for the communication of regional weather events against the backdrop of global warming.”
Data science methods not only allow researchers to demonstrate the strength of the human “fingerprint,” they also show where in the world climate change is particularly clear and recognizable at an early stage. This is important in the hydrological cycle, where there are very large natural fluctuations from day to day and year to year.
“In future, we should therefore be able to pick out human-induced patterns and trends in other more complex measurement parameters, such as precipitation, that are hard to detect using traditional statistics,” says Knutti.
The research appears in Nature Climate Change.
About the Authors
A group led by Reto Knutti, a professor in the environmental systems sciences department at ETH Zurich. Includes lead author Sebastian Sippel.
Climate Change: What Everyone Needs to Know
by Joseph Romm
The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon
Climate Change: The Science of Global Warming and Our Energy Future second edition Edition
by Jason Smerdon
This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena. Available On Amazon
The Science of Climate Change: A Hands-On Course
by Blair Lee, Alina Bachmann
The Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.