Amplification of Surface Temperature Trends and Variability in the Tropical Atmosphere

Abstract

26. We chose these values of the target factors to produce our final results because we have concluded that they are the most likely to be free of errors. They are calculated from oceanic observations to reduce errors from uncorrected diurnal variations, and we use unweighted MSU channel 2 data (T2 in SOM) to avoid additional noise due to the differencing procedure used to calculate TLT. The values of the intersatellite offsets needed to be recalculated to remove obvious intersatellite differences. In the supporting online material, we discuss the impact of using different data subsets to determine the target factors. This information is used to help determine the structural uncertainty. 27. We obtain this estimate of the tropical TLT trend when we recalculate the intersatellite offsets to optimize them for tropical data. If this reoptimization is not performed, as it is not in producing maps such as those shown in Fig. 3, we obtain a smaller trend value of 0. The month-to-month variability of tropical temperatures is larger in the troposphere than at Earth's surface. This amplification behavior is similar in a range of observations and climate model simulations and is consistent with basic theory. On multidecadal time scales, tropospheric amplification of surface warming is a robust feature of model simulations, but it occurs in only one observational data set. Other observations show weak, or even negative, amplification. These results suggest either that different physical mechanisms control amplification processes on monthly and decadal time scales, and models fail to capture such behavior; or (more plausibly) that residual errors in several observational data sets used here affect their representation of long-term trends.Tropospheric warming is a robust feature of climate model simulations that include historical increases in greenhouse gases (1-3). Maximum warming is predicted to occur in the middle and upper tropical troposphere. Atmospheric temperature measurements from radiosondes also show warming of the tropical troposphere since the early 1960s (4-7), consistent with model results (8). The observed tropical warming is partly due to a step-like change in the late 1970s (5, 6). Considerable attention has focused on the shorter record of satellite-based atmospheric temperature measurements (1979 to present). In both models and observations, the tropical surface warms over this period. Simulated surface warming is amplified in the tropical troposphere, corresponding to a decrease in lapse rate (2,3,9). In contrast, a number of radiosonde and satellite data sets suggest that the tropical troposphere has warmed less than the surface, or even cooled, which would correspond to an increase in lapse rate (4)(5)(6)(7)(8)(9)(10)(11)(12).This discrepancy may be an artifact of residual inhomogeneities in the observations (13)(14)(15)(16)(17)(18)(19). Creating homogeneous climate records requires the identification and removal of nonclimatic influences from data that were primarily collected for weather forecasting...

Assessing Bias and Uncertainty in the HadAT-Adjusted Radiosonde Climate Record

“…For comparison the radiosonde datasets have been vertically averaged with weightings to create equivalent MSU retrieved bulk temperatures for T4 (stratosphere), T2 (troposphere), and T2LT (lower troposphere). For reference we also show the trend from the Hadley Centre Climatic Research Unit, version 3 (HadCRUT3), surface records (Brohan et al 2006), and theoretical expectation from an ensemble of climate models (Santer et al 2005). Figure 9 shows the spread of trend estimates from this ensemble of homogenizations for the tropical satellite era.…”

“…However, when considering the more recent satellite era (1979 onward), the same radiosonde datasets indicate that the troposphere is warming at a slower rate than at the surface, particularly within the tropics. This is at odds with climate models, which predict amplification of the surface trends in the tropics (Santer et al 2005;Karl et al 2006). Some Microwave Sounding Unit (MSU) satellite records indicate similar changes in the troposphere to radiosonde records (Christy and Norris 2006), whereas others are in broad agreement with the model predictions (Mears and Wentz 2005;Vinnikov et al 2006).…”

Science prizes: Best in class

“…Led by Santer, a large team including many highprofile climate scientists, then showed that the new data set was in good agreement with computer models 4 .…”

On the Estimates of Tropospheric Temperature Anomalies in 2015-2016

“…Ряды на основе радиозондо-вых данных демонстрируют существенное понижение температуры тропосферы в период до середины 1970-х годов. Это понижение лишь начи-ная со второй половины 1970-х годов после хорошо известного из литературы скачкообразного повышения температуры тропосферы, связываемого с пере-стройкой циркуляционных режимов Северного полушария (Santer et al, 2005), сменилось последовательным потеплением. …”

“…На изменения и колебания температуры в тропосфере влияние оказы-вают как вызванные человеческой деятельностью процессы выброса парниковых газов, так и процессы в системе «океан-атмосфера» временного масштаба нескольких лет, в частности, положительные и отрицательные фазы явления Эль-Ниньо. Влияние же особенностей рельефа, свойств подсти-лающей поверхности на температуру в тропосфере менее значительно, чем на приземную температуру, поэтому рядом авторов (Santer et al, 2005) выска-заны предположения о «меньшей зашумленности» сигнала температуры в тропосфере по сравнению с сигналом приземной температуры.…”