Global warming: Evidence for asymmetric diurnal temperature change

Abstract

Analyses of the year‐month mean maximum and minimum surface thermometric record have now been updated and expanded to cover three large countries in the Northern Hemisphere (the contiguous United States, the Soviet Union, and the People's Republic of China). They indicate that most of the warming which has occurred in these regions over the past four decades can be attributed to an increase of mean minimum (mostly nighttime) temperatures. Mean maximum (mostly daytime) temperatures display little or no warming. In the USA and the USSR (no access to data in China) similar characteristics are also reflected in the changes of extreme seasonal temperatures, e.g., increase of extreme minimum temperatures and little or no change in extreme maximum temperatures. The continuation of increasing minimum temperatures and little overall change of the maximum leads to a decrease of the mean (and extreme) temperature range, an important measure of climate variability. The cause(s) of the asymmetric diurnal changes are uncertain, but there is some evidence to suggest that changes in cloud cover plays a direct role (where increases in cloudiness result in reduced maximum and higher minimum temperatures). Regardless of the exact cause(s), these results imply that either: (1) climate model projections considering the expected change in the diurnal temperature range with increased levels of the greenhouse gases are underestimating (overestimating) the rise of the daily minimum (maximum) relative to the maximum (minimum), or (2) the observed warming in a considerable portion of the Northern Hemisphere landmass is significantly affected by factors unrelated to an enhanced anthropogenically‐induced greenhouse effect.

Rice yields decline with higher night temperature from global warming

“…1 A and B). The increase in minimum temperature was 3.2 times greater than the increase in maximum temperature, which is consistent with the observation that minimum temperature has increased approximately three times as much as (10). However, the magnitude of increase at our site was greater than the global trend determined over the 1950-1993 period (11).…”

“…In the past century, daily minimum nighttime temperature increased at a faster rate than daily maximum temperature in association with a steady increase in atmospheric greenhouse gas concentrations (10,11). Although the effects of projected climate change on crop yields have been evaluated by using crop-simulation models (8), there are few studies on the effects of observed climate change on crop growth and yield (12,13).…”

Human contribution to climate change remains questionable

“…Observations indicate that the diurnal temperature range has been decreasing in the Northern Hemisphere and perhaps in the Southern Hemisphere as well [Karl et al, 1991].These could be traced to possible increases in aerosols or cloudiness. There is evidence also for winter warming, but not yet for the expected warming at high latitudes predicted by the climate models.…”

Effects of diurnal warming on soil respiration are not equal to the summed effects of day and night warming in a temperate steppe

“…However, many uncertainties remain to be addressed. For example, historical meteorological records and model projections reveal a warming trend that is more pronounced at night than day (Karl et al, 1991;Easterling et al, 1997;IPCC, 2001;Zhou et al, 2007). Although such an asymmetric diurnal warming is still under debate (Vose et al, 2005;IPCC, 2007), it has been widely observed over the land surface since 1950 (Easterling et al, 1997;Zhou et al, 2007).…”