Changes in global blocking character in recent decades

A global blocking climatology published by this group for events that occurred during the late 20th century examined a comprehensive list of characteristics that included block intensity (BI). In addition to confirming the results of other published climatologies, they found that Northern Hemisphere (NH) blocking events (1968-1998) were stronger than Southern Hemisphere (SH) blocks and winter events are stronger than summer events in both hemispheres. This work also examined the interannual variability of blocking as related to El Niño and Southern Oscillation (ENSO). Since the late 20th century, there is evidence that the occurrence of blocking has increased globally. A comparison of blocking characteristics since 1998 (1998-2018 NH; 2000-2018 SH) shows that the number of blocking events and their duration have increased significantly in both hemispheres. The blocking BI has decreased by about six percent in the NH, but there was little change in the BI for the SH events. Additionally, there is little or no change in the primary genesis regions of blocking. An examination of variability related to ENSO reveals that the NH interannual-scale variations found in the earlier work has reversed in the early 21st century. This could either be the result of interdecadal variability or a change in the climate. Interdecadal variations are examined as well

Chapter 10 - Detection and attribution of climate change: From global to regional

This chapter assesses the causes of observed changes assessed in Chapters 2 to 5 and uses understanding of physical processes, climate models and statistical approaches. The chapter adopts the terminology for detection and attribution proposed by the IPCC good practice guidance paper on detection and attribution (Hegerl et al., 2010) and for uncertainty Mastrandrea et al. (2011). Detection and attribution of impacts of climate changes are assessed by Working Group II, where Chapter 18 assesses the extent to which atmospheric and oceanic changes influence ecosystems, infrastructure, human health and activities in economic sectors

Model Estimates of Global and Regional Climate Changes in the Holocene

© 2020, Pleiades Publishing, Ltd. Abstract: On the basis of simulations using a global climate model, the global and regional climate changes in the Holocene are estimated. According to our results, the average contemporary level of global near-surface temperature in recent decades exceeded the respective values during the last 10 kyr, including the period of the Holocene optimum (Middle Holocene, about 6 kyr B.P.). However, modern temperature regimes in particular regions (e.g., Europe) may be below the maximum warming level of the Middle Holocene. Global and regional climate changes and variations in the carbon cycle characteristics over the last century (based on model calculations, with the anthropogenic effect being taken into account) considerably differ from the variations in the preceding centuries and millennia, when natural impacts on the climate system played the key role