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New study shows human influences increase the amplitude of seasonal cycle

AgWeb posted an interesting article this week on a new study published by scientists at Lawrence Livermore National Laboratory on trends in the seasonal cycle of temperatures around the globe. The work used a new technique called “fingerprinting” which allowed them to separate out the effects of natural climate variability such as that caused by El Niño or volcanic activity from the effects caused by human influences like the increase in carbon dioxide or land use changes. The study shows that for most of the globe, the amplitude of the seasonal cycle has been increasing in the period from 1979 to 2016. That means that the temperature differences between the coldest  and warmest months is increasing. The increases are due primarily to increasing warm season temperatures, which are linked to drier conditions which allow temperatures to soar. You can read the AgWeb article here.

Trends in the amplitude of the annual cycle of tropospheric temperature. Trends are calculated over 1979 to 2016 and are averages from a large multi-model ensemble of historical simulations. The most prominent features are pronounced mid-latitude increases in annual cycle amplitude (shown in the red colors) in both hemispheres. Similar mid-latitude increases occur in satellite temperature data. Trends are superimposed on NASA’s “blue marble” image.