David H. Douglass

What Do Observational Datasets Say about Modeled Tropospheric Temperature Trends since 1979

Updated tropical lower tropospheric temperature datasets covering the period 1979–2009 are presented and assessed for accuracy based upon recent publications and several analyses conducted here. We conclude that the lower tropospheric temperature (TLT) trend over these 31 years is +0.09 ± 0.03 °C decade−1. Given that the surface temperature (Tsfc) trends from three different groups agree extremely closely among themselves (~ +0.12 °C decade−1) this indicates that the “scaling ratio” (SR, or ratio of atmospheric trend to surface trend: TLT/Tsfc) of the observations is ~0.8 ± 0.3. This is significantly different from the average SR calculated from the IPCC AR4 model simulations which is ~1.4. This result indicates the majority of AR4 simulations tend to portray significantly greater warming in the troposphere relative to the surface than is found in observations. The SR, as an internal, normalized metric of model behavior, largely avoids the confounding influence of short-term fluctuations such as El Ninos which make direct comparison of trend magnitudes less confident, even over multi-decadal periods.

Disparity of tropospheric and surface temperature trends: New evidence

Received 9 April 2004; revised 27 May 2004; accepted 7 June 2004; published 9 July 2004. [1] Observations suggest that the earth’s surface has been warming relative to the troposphere for the last 25 years; this is not only difficult to explain but also contrary to the results of climate models. We provide new evidence that the disparity is real. Introducing an additional data set, R2 2-meter temperatures, a diagnostic variable related to tropospheric temperature profiles, we find trends derived from it to be in close agreement with satellite measurements of tropospheric temperature. This suggests that the disparity likely is a result of near-surface processes. We find that the disparity does not occur uniformly across the globe, but is primarily confined to tropical regions which are primarily oceanic. Since the ocean measurements are sea surface temperatures, we suggest that the disparity is probably associated with processes at the ocean-atmosphere interface. Our study thus makes unlikely some of the explanations advanced to account for the disparity; it also demonstrates the importance of distinguishing between land, sea and air measurements. INDEX TERMS: 1610 Global Change: Atmosphere (0315, 0325); 1699 Global Change: General or miscellaneous; 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 4504 Oceanography: Physical: Air/sea interactions (0312). Citation: Douglass, D. H., B. D. Pearson, S. F. Singer, P. C. Knappenberger, and P. J. Michaels (2004), Disparity of tropospheric and surface temperature trends: New evidence, Geophys. Res. Lett., 31, L13207, doi:10.1029/ 2004GL020212.

Temperature response of Earth to the annual solar irradiance cycle

Abstract We directly determine the sensitivity and time delay of Earths surface temperature response to annual solar irradiance variations from 60 years of data. A two-layer energy balance model is developed to interpret the results. Explaining both the resulting low sensitivity and time delay of 1–2 months requires negative feedback.

Limits on CO2 Climate Forcing from Recent Temperature Data of Earth

The global atmospheric temperature anomalies of Earth reached a maximum in 1998 which has not been exceeded during the subsequent 10 years. The global anomalies are calculated from the average of climate effects occurring in the tropical and the extratropical latitude bands. El Niño/La Niña effects in the tropical band are shown to explain the 1998 maximum while variations in the background of the global anomalies largely come from climate effects in the northern extratropics. These effects do not have the signature associated with CO2 climate forcing. However, the data show a small underlying positive trend that is consistent with CO2 climate forcing with no-feedback.

Bounded regions of chaotic behavior in the control parameter space of a driven non-linear resonator

Abstract We have investigated the behavior of a driven non-linear electrical resonator over a large region of the control parameter space, i.e. the amplitude and frequency of the drive voltage. In addition to features characteristic of a one-dimensional non-invertible iterated map there exist isolated regions of chaotic behavior bounded by a Feigenbaum series of period-doubling bifurcations.

Reconciling Observations of Global Temperature Change: 2013

In 2000 a panel of the U.S. National Research Council in a report with the same title suggested, among other things, that a “substantial disparity remains” between the observed warming rates of the surface and troposphere. Also, in 2000, the climate models showed more warming of the tropical atmosphere than was observed. Many papers have been written since then. We discuss the most recent papers on this subject and using the latest data show that the differences remain unresolved.

Reply to comment by A. Robock on “Climate forcing by the volcanic eruption of Mount Pinatubo”

[1] In our Pinatubo paper [Douglass and Knox, 2005a, hereinafter referred to as DK] we concluded that there was negative climate feedback and a short climate response time. Robock [2005, hereinafter referred to as R] claims that the outgoing long-wave radiation (LW) was incorrectly described as the forcing and that interchange of energy with the thermocline was unjustifiably neglected in determining our results. Although we made certain incorrect statements about the LW radiation, these were not part of our determination of the parameters. As to energy flow to the thermocline, as we argue elsewhere [Douglass and Knox, 2005b, hereinafter referred to as DK2], this flow is estimated be small and to affect our lifetime and sensitivities by less than 15%, not by a factor of three, as claimed.

Internal friction measurements in Boron-doped single-crystal silicon

Abstract Internal friction measurements, Q −1 , of a boron-doped single crystal of silicon at a frequency ω = 2 π × 29.2 kHz showed: (1) results in agreement with the Akhieser mechanism above 100 K; and (2) Q -1 ∝ ω T −1 at temperatures below 10 K.

Reply to comments by H. Bjornsson et al. on “Iceland as a heat island”

[1] Bjornsson et al. [2005] (hereinafter referred to as BJJ) make two critical points about our paper on Iceland [Douglass et al., 2005]. The first is that BJJ’s own analysis of temperature trends in Iceland ‘‘does not support [our] conclusions’’ that ‘‘recent temperature increases in Iceland are due to variations in thermal heating.’’ The second is that one of BJJ’s maps is not the same as our corresponding map, despite having originated in the same data set. The authors’ first point is moot, because they only reinforce our actual findings. Below we briefly discuss, but do not immediately resolve, the map problem. [2] In the paper we note that Iceland’s considerable geothermal activity suggests a connection to the observed data, but after pointing out the quantitative inadequacy of the geothermal hypothesis we state ‘‘. . .the temperature trends we observe must be due to complex persistent microclimate effects that do not conform to simple forcing theory and which involve quite large positive feedbacks.’’ Even in our introduction, we point out the quantitative results and refer to them as ‘‘an unresolved puzzle.’’ BJJ also refer to our observation of the extended nature of the warming trend as a ‘‘contention that the geothermally enhanced warming extends over an area far larger than Iceland. . .’’ (emphasis ours). This was neither said nor implied in our paper. The large extent of the warming trend was presented as observed fact, not ‘‘contention,’’ and with no specific claim that the warming was ‘‘geothermally enhanced.’’ The mapping discrepancy may be related to different methods of data conversions from the original Gaussian grid to a 2.5 2.5 grid. Our published map was produced by a bilinear interpolation program GG2LL, which is found at the web site containing the NCEP data [Kistler et al., 2001] (data available at http://dss.ucar.edu/ datasets/ds090.2/data/monthly/). We are looking into the discrepancy further, and at this time can remark only that either version of the 2-m map under discussion is generally consistent with both our higher-altitude maps and our conclusions. [3] We welcome BJJ’s alternative hypothesis that changes in sea ice cover may have caused the large observed warming trend. Indeed one of the purposes of our paper was to call attention to this interesting anomaly. One hopes that the extensive literature quoted by the authors can produce a quantitative explanation. We are not ready to accept the authors’ hypothesis that the local anomaly is simply part of a global warming trend, especially as it applies to the time period we studied. As shown by Douglass et al.’s [2005] Figures 1a and 1b, the anomaly in question is unique to latitudes at and above that of Iceland. [4] We take this opportunity to remind readers that the observed anomalies are not simply at the surface. A finding that tends to be obscured by this discussion was that the 1979–1996 anomaly has an altitude effect whose existence implies a strong long-term correlation in warming and cooling processes at different altitudes. The sea-ice hypothesis may be consistent with this, but a quantitative explanation remains to be found.

Comment on “Can slow variations in solar luminosity provide missing link between the Sun and climate?”

Peter Foukal (Eos, 3 June 2003) has written an interesting and informative article on solar luminosity and climate. He mentions recent evidence correlating solar activity to climate changes during the last millennium and the last Ice Age and discusses possible mechanisms. He also presents the case for the importance of determining the correlation between solar variation and climate. Foukals discussion is mainly about “slow variations,” which appears to mean centennial-to-millennial time scales. However, in the “Future Direction” section, he discusses the desirability of the determination of the “climate sensitivity to the small irradiance changes so far observed [1979 to present].”