Thomas R. Karl

Bio: Thomas R. Karl is an academic researcher from National Oceanic and Atmospheric Administration. The author has contributed to research in topics: Climate change & Global warming. The author has an hindex of 86, co-authored 170 publications receiving 37213 citations.

Climate Extremes: Observations, Modeling, and Impacts

Abstract: One of the major concerns with a potential change in climate is that an increase in extreme events will occur. Results of observational studies suggest that in many areas that have been analyzed, changes in total precipitation are amplified at the tails, and changes in some temperature extremes have been observed. Model output has been analyzed that shows changes in extreme events for future climates, such as increases in extreme high temperatures, decreases in extreme low temperatures, and increases in intense precipitation events. In addition, the societal infrastructure is becoming more sensitive to weather and climate extremes, which would be exacerbated by climate change. In wild plants and animals, climate-induced extinctions, distributional and phenological changes, and species' range shifts are being documented at an increasing rate. Several apparently gradual biological changes are linked to responses to extreme weather and climate events.

Modern Global Climate Change

Abstract: Modern climate change is dominated by human influences, which are now large enough to exceed the bounds of natural variability. The main source of global climate change is human-induced changes in atmospheric composition. These perturbations primarily result from emissions associated with energy use, but on local and regional scales, urbanization and land use changes are also important. Although there has been progress in monitoring and understanding climate change, there remain many scientific, technical, and institutional impediments to precisely planning for, adapting to, and mitigating the effects of climate change. There is still considerable uncertainty about the rates of change that can be expected, but it is clear that these changes will be increasingly manifested in important and tangible ways, such as changes in extremes of temperature and precipitation, decreases in seasonal and perennial snow and ice extent, and sea level rise. Anthropogenic climate change is now likely to continue for many centuries. We are venturing into the unknown with climate, and its associated impacts could be quite disruptive.

Maximum and Minimum Temperature Trends for the Globe

Abstract: Analysis of the global mean surface air temperature has shown that its increase is due, at least in part, to differential changes in daily maximum and minimum temperatures, resulting in a narrowing of the diurnal temperature range (DTR). The analysis, using station metadata and improved areal coverage for much of the Southern Hemisphere landmass, indicates that the DTR is continuing to decrease in most parts of the world, that urban effects on globally and hemispherically averaged time series are negligible, and that circulation variations in parts of the Northern Hemisphere appear to be related to the DTR. Atmospheric aerosol loading in the Southern Hemisphere is much less than that in the Northern Hemisphere, suggesting that there are likely a number of factors, such as increases in cloudiness, contributing to the decreases in DTR.

A new look at maximum and minimum temperature trends for the globe

Abstract: A number of recent studies have established that differential changes in daily maximum and minimum temperatures are occurring, resulting in changes in the diurnal temperature range (DTR) for many parts of the globe. Large-scale trends in the USA indicate that minimum temperatures are increasing at a faster rate than maximum temperatures, resulting in a narrowing in the DTR. This paper updates and extends the analysis of changes in the DTR in three ways: (1) by increasing the areal coverage to more than half the global landmass, (2) by addressing the issue of homogeneity of the data, and (3) by examining the potential effects of urban stations on the calculated trends. The update includes data for an additional 15% of the global land area and an extension of the analysis period used in a previous study. Homogeneity techniques were used on the data to adjust individual station data for undocumented discontinuities. Annual maximum and minimum temperature and DTR time series for the 1950-1993 period averaged over 54% of the total global land area are presented. The trend for the maximum temperature is 0.88 C/100 years, which is consistent with earlier findings. However, the trend for the minimum temperature is 1.86 C/100more » years; this is less than found in previous analyses and leads to a smaller trend in the DTR. This finding is not surprising since much of the data added in this study are for tropical and sub-tropical regions where temperature trends are not expected to be as large as in higher latitude regions. The effect of urbanization on the global trends is found to be on the order of 0.1 C/100 years or less, which is consistent with previous investigations. 14 refs., 2 figs.« less

Secular Trends of Precipitation Amount, Frequency, and Intensity in the United States

Abstract: Twentieth century trends of precipitation are examined by a variety of methods to more fully describe how precipitation has changed or varied Since 1910, precipitation has increased by about 10% across the contiguous United States The increase in precipitation is reflected primarily in the heavy and extreme daily precipitation events For example, over half (53%) of the total increase of precipitation is due to positive trends in the upper 10 percentiles of the precipitation distribution These trends are highly significant, both practically and statistically The increase has arisen for two reasons First, an increase in the frequency of days with precipitation ]6 days (100 yr)−1[ has occurred for all categories of precipitation amount Second, for the extremely heavy precipitation events, an increase in the intensity of the events is also significantly contributing (about half) to the precipitation increase As a result, there is a significant trend in much of the United States of the highest

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

A globally coherent fingerprint of climate change impacts across natural systems

Abstract: Causal attribution of recent biological trends to climate change is complicated because non-climatic influences dominate local, short-term biological changes. Any underlying signal from climate change is likely to be revealed by analyses that seek systematic trends across diverse species and geographic regions; however, debates within the Intergovernmental Panel on Climate Change (IPCC) reveal several definitions of a 'systematic trend'. Here, we explore these differences, apply diverse analyses to more than 1,700 species, and show that recent biological trends match climate change predictions. Global meta-analyses documented significant range shifts averaging 6.1 km per decade towards the poles (or metres per decade upward), and significant mean advancement of spring events by 2.3 days per decade. We define a diagnostic fingerprint of temporal and spatial 'sign-switching' responses uniquely predicted by twentieth century climate trends. Among appropriate long-term/large-scale/multi-species data sets, this diagnostic fingerprint was found for 279 species. This suite of analyses generates 'very high confidence' (as laid down by the IPCC) that climate change is already affecting living systems.

Ecological responses to recent climate change.

Abstract: There is now ample evidence of the ecological impacts of recent climate change, from polar terrestrial to tropical marine environments. The responses of both flora and fauna span an array of ecosystems and organizational hierarchies, from the species to the community levels. Despite continued uncertainty as to community and ecosystem trajectories under global change, our review exposes a coherent pattern of ecological change across systems. Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible.

Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century

Abstract: [1] We present the Met Office Hadley Centre's sea ice and sea surface temperature (SST) data set, HadISST1, and the nighttime marine air temperature (NMAT) data set, HadMAT1. HadISST1 replaces the global sea ice and sea surface temperature (GISST) data sets and is a unique combination of monthly globally complete fields of SST and sea ice concentration on a 1° latitude-longitude grid from 1871. The companion HadMAT1 runs monthly from 1856 on a 5° latitude-longitude grid and incorporates new corrections for the effect on NMAT of increasing deck (and hence measurement) heights. HadISST1 and HadMAT1 temperatures are reconstructed using a two-stage reduced-space optimal interpolation procedure, followed by superposition of quality-improved gridded observations onto the reconstructions to restore local detail. The sea ice fields are made more homogeneous by compensating satellite microwave-based sea ice concentrations for the impact of surface melt effects on retrievals in the Arctic and for algorithm deficiencies in the Antarctic and by making the historical in situ concentrations consistent with the satellite data. SSTs near sea ice are estimated using statistical relationships between SST and sea ice concentration. HadISST1 compares well with other published analyses, capturing trends in global, hemispheric, and regional SST well, containing SST fields with more uniform variance through time and better month-to-month persistence than those in GISST. HadMAT1 is more consistent with SST and with collocated land surface air temperatures than previous NMAT data sets.