Predictability of weather and climate

Abstract:

Anthropogenic greenhouse gas emissions significantly impact the middle and upper atmosphere. They cause cooling and thermal shrinking and affect the atmospheric structure. Atmospheric contraction results in changes in key atmospheric features, such as the stratopause height or the peak ionospheric electron density, and also results in reduced thermosphere density. These changes can impact, among others, the lifespan of objects in low Earth orbit, refraction of radio communication and GPS signals, and the peak altitudes of meteoroids entering the Earth's atmosphere. Given this, there is a critical need for observational capabilities to monitor the middle and upper atmosphere. Equally important is the commitment to maintaining and improving long‐term, homogeneous data collection. However, capabilities to observe the middle and upper atmosphere are decreasing rather than improving.

Abstract:

Significant changes have occurred during the last few decades across the North Atlantic climate system, including in the atmosphere, ocean, and cryosphere. These large-scale changes play a vital role in shaping regional climate and extreme weather events across the UK and Western Europe. This review synthesizes the characteristics of observed large-scale changes in North Atlantic atmospheric and oceanic circulations during past decades, identifies the drivers and physical processes responsible for these changes, outlines projected changes due to anthropogenic warming, and discusses the predictability of these circulations. On multi-decadal time scales, internal variability, anthropogenic forcings (especially greenhouse gases), and natural forcings (such as solar variability and volcanic eruptions) are identified as key contributors to large-scale variability in North Atlantic atmospheric and oceanic circulations. However, there remain many uncertainties regarding the detailed characteristics of these various influences, and in some cases their relative importance. We therefore conclude that a better understanding of these drivers, and more accurate quantification of their relative roles, are crucial for more reliable decadal predictions and projections of regional climate for the North Atlantic and Europe.Supplementary informationThe online version contains supplementary material available at 10.1007/s00382-025-07591-1.

Abstract:

Circumglobal teleconnections from wave-like patterns in the mid-latitude jets can lead to synchronized weather extremes in the mid-latitudes of Northern and Southern hemispheres. The simultaneous occurrence of record breaking and persistent northern hemisphere temperature anomalies in Summer 2018 were previously discussed in the context of a persistent zonally elongated wave-7 pattern that stretched over large parts of the northern hemisphere over an extended time and let to considerable societal impacts. Various diagnostics have been put forward to quantify and detect such wave patterns, many of which incorporate low-pass time filtering to separate signal from noise. In this response we argue that advancing our understanding of the large-scale circulation’s response to anthropogenic climate change and reducing associated uncertainties in future climate risk requires a diverse range of perspectives and diagnostics from both the climate and weather research communities.