T.R. Karl

Intensity-duration-frequency (IDF) curves – sometimes also called precipitation frequency estimates – are used to design urban drainage systems for stormwater control and, when combined with hydrologic modeling, to design flood control infrastructure and other structures. However, common approaches to estimating IDF curves need to be revised to acc...

An analysis of 3,104 stations in the United States shows virtually every station exhibits a positive correlation between precipitable water (PW) and extreme daily precipitation (EP) with over one‐third statistically significant. To first approximation, EP scales linearly with PW, but there is nonlinear scaling at the lower and upper ends of the PW...

Trends of extreme precipitation (EP) using various combinations of average return intervals (ARIs) of 1, 2, 5, 10, and 20 years with durations of 1, 2, 5, 10, 20, and 30 days were calculated regionally across the contiguous U.S. Changes in the sign of the trend of EP vary by region as well as ARI and duration, despite the statistically significant...

Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of s...

Global mean surface temperatures (GMST) exhibited a smaller rate of warming during 1998–2013, compared to the warming in the latter half of the 20th Century. Although, not a “true” hiatus in the strict definition of the word, this has been termed the “global warming hiatus” by IPCC (2013). There have been other periods that have also been defined a...

Many climate studies assess trends and projections in heavy precipitation events using precipitation percentile (or quantile) indices. Here we investigate three different percentile indices that are commonly used. We demonstrate that these may produce very different results and thus require great care with interpretation. More specifically, conside...

Global trends of sea surface temperature (SST) are assessed for the existing and new experimental SST analyses that incorporate Advanced Very High Resolution Radiometer (AVHRR) observations from NOAA polar orbiting satellites. These analyses show that globally and annually averaged SST trends over the 21st Century (2000-2015) are similar to the tre...

OS44A

Two scales of mixed Rossby-gravity (MRG) and Kelvin waves in the lower stratosphere are identified through space time spectral, cross spectral and Principal Component analysis of filtered dynamical fields from radiosonde and reanalysis data. A standard covariance matrix EOF analysis of filtered wind along the equator at 50 hPa is used to isolate MR...

Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming "hiatus." Here we present an updated global surface temperature analysis that reveals that global trends are higher than reported by the IPCC, especially in re...

We welcome the comments of Landsea (2015, hereafter L15) and we1 applaud his efforts toward reanalyzing past tropical cyclone data in the Atlantic (Landsea et al. 2008, 2012, 2014; Hagen et al. 2012). However, L15 does not substantially change the conclusions stated in Kunkel et al. (2013, hereafter K13). L15 voices two main concerns: 1. The U.S. l...

The 100 most severe snowstorms within each of six climate regions east of the Rocky Mountains were analyzed to understand how the frequency of severe snowstorms is associated with seasonal averages of other variables that may be more readily predicted and projected. In particular, temperature, precipitation, and El Nino/La Nina anomalies from 1901...

This scientific assessment examines changes in three climate extremes (extratropical storms, winds, and waves), with an emphasis on U.S. coastal regions during the cold season. There is moderate evidence of an increase in both extratropical storm frequency and intensity during the cold season in the Northern Hemisphere since 1950, with suggestive e...

Precipitation changes in a warmer world for major grain growing regions Precipitation is a primary driver for crops grown around the world. What do we know about future seasonal precipitation amount in the major grain growing areas in a warmer world? The literature on this can be confusing, as many meteorological factors control seasonal precipita...

Air and water quality are impacted by extreme weather and climate events on time scales ranging from minutes to many months. This review paper discusses the state of knowledge of how and why extreme events are changing and are projected to change in the future. These events include heat waves, cold waves, floods, droughts, hurricanes, strong extrat...

[1] Annual rankings of global temperature are an important component of climate monitoring. However, there is some degree of uncertainty for every yearly value in the global temperature time series, which leads to uncertainty in annual rankings as well. This study applies a Monte Carlo uncertainty analysis to the National Oceanic and Atmospheric Ad...

The U.S. economy has grown to be the world's largest, even in the face of the most varied and costly weather and climate extremes on the planet (see http://www.munichreamerica.com/webinars/2013_01_natcatreview/MunichRe_III_NatCat01032013.pdf). Nevertheless, these extremes continue to take a toll on the nation, diverting public and private funds whi...

Weather and climate extremes have been varying and changing on many different time scales. In recent decades, heat waves have generally become more frequent across the United States, while cold waves have been decreasing. While this is in keeping with expectations in a warming climate, it turns out that decadal variations in the number of U.S. heat...

The climate record from many parts of North America provides ample evidence of climate change. For specific elements such as temperature or precipitation, a substantial portion of these changes can be shown to be statistically significant; that is, they either reflect an unusual combination of events in a stationary process or they reflect a nonsta...

Observations of planet Earth and especially all climate system components and forcings are increasingly needed for planning and decision making related to climate services in the broadest sense. Although significant progress has been made, much more remains to be done before a fully functional climate observing system exists. Observations are neede...

Probable maximum precipitation (PMP) is the greatest accumulation of precipitation for a given duration meteorologically possible for an area. Climate change effects on PMP are analyzed, in particular, maximization of moisture and persistent upward motion, using both climate model simulations and conceptual models of relevant meteorological systems...

The performance of US national climate reference network was assessed after operating for ten years. The US Climate Reference Network (USCRN) performed the task of benchmarking source of climate data on behalf of the decision makers. The USCRN was conceived in response to these challenges of station changes to the climate record. The main goal of t...

The state of knowledge regarding trends and an understanding of their causes is presented for a specific subset of extreme weather and climate types. For severe convective storms (tornadoes, hailstorms, and severe thunderstorms), differences in time and space of practices of collecting reports of events make using the reporting database to detect t...

As a major exporter of food, the U.S. has a critical interest in carefully monitoring and projecting changes in extreme events as a vital part of an effective strategy to ensure global food security. A variety of indicators have been calculated for extremes of temperature, drought, and precipitation. Many of these indicators now reveal significant...

Given the increases in spatial resolution and other improvements in climate modeling capabilities over the last decade since the CMIP3 simulations were completed, CMIP5 provides a unique opportunity to assess scientific understanding of climate variability and change over a range of historical and future conditions. With participation from over 20...

The spring and summer (March through August) of 2011-2012 set many new climatological records across the contiguous United States, including the hottest month in the instrumental record: July 2012. Various measures of temperature extremes and drought severity serve to put this period into historical perspective (1895 to present) and to assess to wh...

Earth’s climate is warming, and destructive weather is growing more prevalent. Coping with the changes will require collaborative science, forward-thinking policy, and an informed public.

In examining intense precipitation over the central United States, the authors consider only days with precipitation when the daily total is above 12.7 mm and focus only on these days and multiday events constructed from such consecutive precipitation days. Analyses show that over the central United States, a statistically significant redistributio...

Stephen Henry Schneider made a difference in our world. His science, his words, and his actions forever changed the way we think about human influences on climate. Stephen Schneider helped us to realize that we are not just innocent bystanders - we are now active agents of change in the climate system. This lecture has two parts. The first part pro...

We compare global-scale changes in satellite estimates of the temperature of the lower troposphere (TLT) with model simulations of forced and unforced TLT changes. While previous work has focused on a single period of record, we select analysis timescales ranging from 10 to 32 years, and then compare all possible observed TLT trends on each timesca...

The demand for long-term, sustained, reliable data and derived information on climate and its changes has never been greater than today. Long-term, well-calibrated, global observations of Essential Climate Variables (ECV) such as air temperature, precipitation, and sea-surface temperature are critical for defining the evolving state of the Earth's...

The design of dams, roads, storm sewers, housing developments, and other types of infrastructure must consider the climatology of extreme precipitation. Probable maximum precipitation (PMP) estimates are needed for reservoir and spillway design where under-design would be catastrophic. Intensity-duration-frequency (IDF) values are used in design si...

In the United States during the past 60 years, the climatology of intense precipitation events, their regional distribution, internal structure (mean and peak hourly intensity and duration) and changes can be analyzed using the long-term time series of dense networks of daily and hourly precipitation gauges. After a major data rescue effort in 2000...

The last 10 years of observational temperature records have received considerable public attention. It has been claimed that the relatively muted surface warming trend of the past decade constitutes 'evidence of absence' of a human effect on climate, and that model simulations of historical climate change are incapable of replicating the observed t...

We perform the most comprehensive comparison to date of simulated and observed temperature trends. Comparisons are made for different latitude bands, timescales, and temperature variables, using information from a multi-model archive and a variety of observational datasets. Our focus is on temperature changes in the lower troposphere (TLT), the mid...

This past year the US Global Change Research Program released a report that summarized the science of climate change and the impacts of climate change on the United States, now and in the future. The report underscores the importance of measures to reduce climate change. In the context of impacts, the report identifies examples of actions currently...

Contemporary climate models send several very different messages regarding changes in the energy and water cycle over northern extratropical land areas that are leading to climate extremes of different kinds. For the regions of the Northern Extratropics with a dense network of long-term time series of daily observations, we quantified several lines...

The National Climatic Data Center (NCDC) recently began executing a new community-based Climate Data Records (CDR) program. The Program provides three core capabilities: 1) POES & GOES Multisatellite Climate Record Development, 2) NPOESS Preparatory Mission (NPP) Climate Record Pre-Processing, and 3) NPOESS/Jason Climate Record Production for “Rema...

The USP provides in plain language a synthesis of our current understanding of global climate change impacts in the United States. It does this by addressing special issues facing a variety of sectors and regions across the United States. In the process of synthesizing this information across a large number of recently completed assessments and new...

The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) concluded that global warming is "unequivocal" and that most of the observed increase since the mid-twentieth century is very likely due to the increase in anthropogenic greenhouse gas concentrations, with discernible human influences on ocean warming, contin...

As part of its climate mandate, NOAA has a responsibility to provide the Nation with objective data and tools to help it characterize, understand, predict, mitigate and adapt to climate change and variability. To help fulfill that responsibility, NOAA has begun coordinating its Climate Data Record (CDR) activities with other agencies through the U....

Coastal sea level rise and fall are governed deterministically by the astronomical tides and stochastically by a host of other factors. Coastal storms occur stochastically. True rates of temporal variability and trends of both sea level variability and storm occurrence, over local to regional scales are not presently identically known, in spite of...

The Nation and broader scientific community have a pressing need for the routine and systematic production of Climate Data Records (CDRs), a position strongly supported through recent reports from the U.S. Climate Change Science Program (CCSP), the Global Climate Observing System (GCOS) and the Intergovernmental Panel on Climate Change (IPCC) Fourt...

A revised framework is presented that quantifies observed changes in the climate of the contiguous United States through analysis of a revised version of the U.S. Climate Extremes Index (CEI). The CEI is based on a set of climate extremes indicators that measure the fraction of the area of the United States experiencing extremes in monthly mean sur...

The NPOESS Program was designed primarily to serve operational users who typically need near real time observations and products. Consequently, NPOESS does not provide reprocessing, data record gap filling, or assurance that its products are consistent with those of heritage missions. However, these characteristics are critical for climate science...

Satellite observations play a critical role in documenting earth system evolution, both in terms of characterizing prior and current evolution of the Earth and providing a baseline against which future measurements can be compared. Given that the construction of the necessary long-term data sets requires the use of multiple instruments on multiple...

This study investigates the frequency of occurrence of tropical cyclones and land-falling hurricanes in the North Atlantic and the Gulf of Mexico over the five telescoping periods of 1851-2006, 1888-2006, 1900-2006, 1950-2006 and 1970-2006. An effort is made to assess the intrinsic modes of variability and trends buried in the data but also to iden...

A Monte Carlo analysis was used to assess the effects of missing data and limited station density on the uncertainties in the temporal variations of U.S. heavy precipitation event frequencies observed for 1895-2004 using data from the U.S. Cooperative Observer Network (COOP). Based on the actual availability of long-term station data, the effects o...

U.S. weather stations operated by NOAA’s National Weather Service (NWS) have undergone significant changes in reporting and measuring cloud ceilings. Stations operated by the Department of Defense have maintained more consistent reporting practices. By comparing cloud-ceiling data from 223 NWS first-order stations with those from 117 military stati...

Significant climatic changes over Northern Eurasia during the 20th century have been reflected in numerous variables of economic, social, and ecological interest, including the natural frequency of forest fires. For the former USSR, we are now using the Global Daily Climatology Network and a new Global Synoptic Data Network archive, GSDN, created j...

The need for data and information that can be used to enhance community resilience to coastal inundation and erosion has been highlighted by the devastating impacts of recent events such as Hurricane Katrina and the 2004 Indian Ocean tsunami. The physical systems causing coastal inundation and erosion are governed by a complex combination of oceani...

The marine atmosphere, coastal ocean, estuary, harbor and river water systems constitute a physically coupled system. While these systems have always been heavily impacted by coastal storms, increases in population density, infrastructure, and personal and business merchandise have exacerbated the economic and personal impacts of these events over...

Model simulations using CO2-induced sea surface temperature increases indicate that TC wind speeds and related daily precipitation may increase. We investigated changes in the TC-related rainfall distributions as a function of TC strength at landfall and impact of SST ahead of TCs on the TC strength for several preferred tropical cyclone regions. O...

A case is made that the national process of special appropriations monies to establish the coastal observing component of the integrated ocean observing system (IOOS) network is not well organized and without substantive value, given the way that it has been orchestrated. Alternatively, a case is made that the special appropriations monies could an...

The climate is changing because of human activities and will continue to do so regardless of any mitigation actions. Available climate observations and information are also changing as technological advances take place. Accordingly, an overview is given of a much-needed potential climate information system that embraces a comprehensive observing sy...

Significant climatic changes over northern Eurasia during the twentieth century are revealed in numerous variables including those affecting and characterizing the state of the cryosphere. In addition to commonly used in situ observations of snow cover such as snow depth and snow courses, synoptic archives in the former Soviet Union contain regular...

A climatological analysis of snowstorms across the contiguous United States, based on data from 1222 weather stations with data during 1901 2001, defined the spatial and temporal features. The average annual incidence of events creating 15.2 cm or more in 1 or 2 days, which are termed as snowstorms, exhibits great spatial variability. The pattern i...

Automated Surface Observation Systems (ASOS) were widely introduced to replace manned weather stations around the mid-1990s over North America and other parts of the world. While laser beam ceilometers of the ASOS in North America measure overhead clouds within the lower 3.6 km of the atmosphere, they do not contain cloud-type and opacity informati...

National Climatic Data Center has recently released several global and regional /national data sets that we designated as baseline data sets. These data have several important features. First, we believe that they can be used for climate change studies. This means that (a) these data sets include long-term time series (at least 50 years of data), (...

The spatial and temporal variability of North Atlantic hurricane tracks and its possible association with the annual hurricane landfall frequency along the U.S. East Coast are studied using principal component analysis (PCA) of hurricane track density function (HTDF). The results show that, in addition to the well-documented effects of the El Niño...

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 sim...

The empirical mode decomposition (EMD) method is used to analyze the nonlin-ear and non-stationary annual cycle (NAC) in climate data. The NAC is defined as an intrinsic mode function generated in the EMD process and has a mean pe-riod equal to a year. Both Hilbert and Fourier spectra of the NAC are examined to validate the power density at the fre...

The annual frequency of western North Pacific (WNP) typhoons and the number of landfall typhoons in China are shown to negatively correlate with the Tibetan Plateau snow cover (TP-SC) during the preceding winter and spring. When TP-SC was above normal, fewer typhoons formed in the WNP and made landfall in China, and vice versa. The observed seasona...

Is the planet getting warmer? Is the hydrologic cycle changing? Is the atmospheric/oceanic circulation changing? Is the weather and climate becoming more extreme or variable? Is the radiative forcing of the climate changing? These are the fundamental questions that must be answered to determine if climate change is occurring. However, providing ans...

Temperature measurements from the U.S. Climate Reference Network (USCRN) instrument system were compared to the Automated Surface Observing System (ASOS) ambient air temperature measurements and were examined under different regimes of wind speed and solar radiation. Influences due to observing practice differences and the effects of siting differe...

Observed changes in intense precipitation (e.g., the frequency of very heavy precipitation or the upper 0.3% of daily precipitation events) have been analyzed for over half of the land area of the globe. These changes have been linked to changes in intense precipitation for three transient climate model simulations, all with greenhouse gas concentr...

An attempt is made to scrutinize Davey and Pielke's recent assessment of site exposures around U.S. Historical Climatology Network (USHCN) stations in eastern Colorado. First, some background on USHCN is given and possible weakness in USHCN site exposure documentation emphasized. Second, the logic behind the application of USHCN in climate change s...

IntroductionIs the Planet Getting Warmer?Is the Hydrologic Cycle Changing?Is the Atmospheric/Oceanic Circulation Changing?Is the Weather and Climate Becoming More Extreme or Variable?Is the Radiative Forcing of the Planet Changing?What Can we do to Improve Our Ability to Detect Climate and Global Changes?

This article describes a spatial prediction method that predicts the monthly sea surface temperature (SST) anomaly field from the land only data. The land data are from the Global Historical Climatology Network (GHCN). The prediction period is 1880–1999 and the prediction ocean domain extends from 60°S to 60°N with a spatial resolution 5°×5°. The p...

Over the contiguous United States, precipitation, temperature, streamflow, and heavy and very heavy precipitation have increased during the twentieth century. In the east, high streamflow has increased as well. Soil wetness (as described by the Keetch-Byram Drought index) has increased over the northern and eastern regions of the United States, but...

Urbanization and other changes in land use have an impact on surface-air temperatures. Kalnay and Cai report that the observed surface-temperature trend in part of the United States exceeds the trend in the NCEP/NCAR 50-year reanalysis (NNR) and conclude that changes in land use account for the difference (0.035 degrees C per decade according to th...

We summarize our research which suggests that changes (mostly increases) in precipitation intensity (heavy and very heavy daily precipitation events) have occurred during the past one hundred years in various regions of the world including the contiguous United States. While the United States constitutes a small fraction of the Earth's surface, it...

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 a...

In support of the U.S. National Assessment of the Potential Consequences of Climate Variability and Change, climate scenarios were prepared to serve as the basis for evaluating the vulnerability of environmental and societal systems to changes projected for the twenty-first century. Since publication of the results of the assessment at the end of 2...

[1] The U.S. Historical Climatology Network (HCN) database contains statistical adjustments that address historical changes in observation time at each observing station in the network. A paper in 2002 suggested that these adjustments cause HCN temperature trends to be “spuriously” warm relative to other datasets for the United States. To test this...

Over the contiguous United States, precipitation, temperature, streamflow (in particular, base streamflow), heavy and very heavy precipitation and high streamflow in the East have increased during the 20th century. In the past 50 years, in addition to these changes, increases in evaporation, near-surface humidity, total, low, and convective cloudin...

Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for i...

Although much has been learned about climate from past and present observing systems, we do not have an adequate climate observing system at present. Instead, we make do with an eclectic mix of observations mostly taken for other purposes. Nor are they adequately synthesized. Hence, in addition to making new observations, there is a strong rational...

more rapidly along this path than is the United States.

A successful global climate monitoring system must fulfill clear societal objectives. For some aspects of climate monitoring, the societal goals are understood and are clearly stated, but long-term, decadal/centennial climate predictions have, in the past, been judged more in terms of curiosity-led criteria. A curiosity-led climate program is not,...

How accurately do climate models reproduce today's climate and that of the past? In their Perspective, Smith et al. compare model errors with observational sampling and analysis errors. The authors find that today's models are within the observed uncertainty, at least with respect to the 100-year record of observed global sea surface temperature....

The output from a large number of model simulations is growing rapidly. This includes model data from Global Climate Models (GCMs), newer "World Models"(with more sophisticated treatment of terrestrial systems, the cryosphere, biogeochemistry, atmospheric chemistry, and/or oceanographic components), reanalysis model simulations, and numerical weath...

We compare the United States and global surface air temperature changes of the past century using the current Goddard Institute for Space Studies (GISS) analysis and the U.S. Historical Climatology Network (USHCN) record [Karl et al., 1990]. Changes in the GISS analysis subsequent to the documentation by Hansen et al. [1999] are as follows: (1) inc...

To determine the sensitivity of the climate to increases in greenhouse gases and other factors, it is important to be able to condidently assess observed changes in global surface temperature. Much has recently been made in the populare press about differences in the rate of temperature change over the oceans as derived from marine surface boundary...