Weather and Climate Extremes in a Changing Climate. Regions of ...

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8 The U.S. Climate Change Science Program Executive Summary Observed changes in North American extreme events, assessment of human influence for the observed changes, and likelihood that the changes will continue through the 6 . W H At M E A S U R E S C A N 21st century1. Phenomenon and direction of change Warmer and fewer cold days and nights Hotter and more frequent hot days and nights More frequent heat waves and warm spells More frequent and intense heavy downpours and higher proportion of total rainfall in heavy precipitation events Increases in area affected by drought More intense hurricanes Where and when these changes occurred in past 50 years Over most land areas, the last 10 years had lower numbers of severe cold snaps than any other 10-year period Over most of North America Over most land areas, most pronounced over northwestern two thirds of North America Over many areas No overall average change for North America, but regional changes are evident Substantial increase in Atlantic since 1970; Likely increase in Atlantic since 1950s; increasing tendency in W. Pacific and decreasing tendency in E. Pacific (Mexico West Coast) since 1980 5 Linkage of human activity to observed changes Likely warmer extreme cold days and nights, and fewer frosts 2 Likely for warmer nights 2 Likely for certain aspects, e.g., nighttime temperatures; & linkage to record high annual temperature 2 Linked indirectly through increased water vapor, a critical factor for heavy precipitation events 3 Likely, Southwest USA. 3 Evidence that 1930’s & 1950’s droughts were linked to natural patterns of sea surface temperature variability Linked indirectly through increasing sea surface temperature, a critical factor for intense hurricanes 5; a confident assessment requires further study 3 Likelihood of continued future changes in this century Very likely 4 Very likely 4 Very likely 4 Very likely 4 Likely in Southwest U.S.A., parts of Mexico and Carribean 4 Likely 4 1Based on frequently used family of IPCC emission scenarios 2Based on formal attribution studies and expert judgment 3Based on expert judgment 4Based on model projections and expert judgment 5As measured by the Power Dissipation Index (which combines storm intensity, duration and frequency)
Weather and Climate Extremes in a Changing Climate Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands 6. WhAT MEASURES CAN bE TAkEN TO IMPROVE ThE UNDERSTANDINg Of WEAThER AND ClIMATE ExTREMES? Drawing on the material presented in this report, opportunities for advancement are described in detail in Chapter 4. Briefly summarized here, they emphasize the highest priority areas for rapid and substantial progress in improving understanding of weather and climate extremes. 1. The continued development and maintenance of high quality climate observing systems will improve our ability to monitor and detect future changes in climate extremes. 2. Efforts to digitize, homogenize and analyze long-term observations in the instrumental record with multiple independent experts and analyses improve our confidence in detecting past changes in climate extremes. 3. Weather observing systems adhering to standards of observation consistent with the needs of both the climate and the weather research communities improve our ability to detect observed changes in climate extremes. 4. Extended recontructions of past climate using weather models initialized with homogenous surface observations would help improve our understanding of strong extratropical cyclones and other aspects of climate variabilty. 5. The creation of annually-resolved, regional-scale reconstructions of the climate for the past 2,000 years would help improve our understanding of very long-term regional climate variability. 6. Improvements in our understanding of the mechanisms that govern hurricane intensity would lead to better short and long-term predictive capabilities. 7. Establishing a globally consistent wind definition for determining hurricane intensity would allow for more consistent comparisons across the globe. 8. Improvements in the ability of climate models to recreate the recent past as well as make projections under a variety of forcing scenarios are dependent on access to both computational and human resources. 9. More extensive access to high temporal resolution data (daily, hourly) from climate model simulations both of the past and for the future would allow for improved understanding of potential changes in weather and climate extremes. 10. Research should focus on the development of a better understanding of the physical processes that produce extremes and how these processes change with climate. 11. Enhanced communication between the climate science community and those who make climate-sensitive decisions would strengthen our understanding of climate extremes and their impacts. 12. A reliable database that links weather and climate extremes with their impacts, including damages and costs under changing socioeconomic conditions, would help our understanding of these events. 9
Page 1 and 2: Weather and Climate Extremes in a C
Page 3 and 4: Weather and Climate Extremes in a C
Page 5 and 6: TABLE OF CONTENTS Synopsis ........
Page 7 and 8: TABLE OF CONTENTS Appendix A ......
Page 9 and 10: Chapter 3 Convening Lead Author: Wi
Page 11 and 12: II SYNOPSIS Weather and Climate Ext
Page 13 and 14: PREFACE Report Motivation and Guida
Page 15 and 16: EXECUTIVE SUMMARY Weather and Clima
Page 17 and 18: ES.1, ES.3, ES.4]). Rates of change
Page 19 and 20: with human-induced increases in gre
Page 21: Weather and Climate Extremes in a C
Page 25 and 26: CHAPTER 1 kEY fINDINgS • • •
Page 27 and 28: Figure 1.1 U.S. Billion Dollar Weat
Page 29 and 30: BOX 1.2: Cold temperature Extremes
Page 31 and 32: Figure 1.4 Probability distribution
Page 33 and 34: For temperature, both the average (
Page 35 and 36: While many changes in timing have b
Page 37 and 38: Figure Box 1.3 Percent of area in t
Page 39 and 40: means of coping with changes and un
Page 41 and 42: societal factors. The National Hurr
Page 43 and 44: planning uses, where possible, the
Page 45 and 46: After particularly severe or visibl
Page 47 and 48: in demographic distributions and we
Page 49 and 50: CHAPTER 2 kEY fINDINgS Observed Cha
Page 51 and 52: 2.1 BACKGROUNd Weather and climate
Page 53 and 54: Analysis of multi-day very extreme
Page 55 and 56: Reductions in Arctic sea ice, espec
Page 57 and 58: in precipitation, the increase in t
Page 59 and 60: Bowl episode but much longer, lasti
Page 61 and 62: fact, there has been little change
Page 63 and 64: mirroring United States changes. Re
Page 65 and 66: from eight stations in southern Son
Page 67 and 68: ainfall may be tied to tropical cyc
Page 69 and 70: to calibrate against existing techn
Page 71 and 72: andom errors in intensity. Taking i
Page 73 and 74:
suggested that these sharp jumps ar
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an increase and are statistically s
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from storm surge and waves farther
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For the 55-year period of 1948-2002
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sity from the mid-1970s to early 19
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Weather and Climate Extremes in a C
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(2007a, 2008) analyzed data from th
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the greatest increases along the sh
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Very snowy seasons (those with seas
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from 1921-1995 indicates that the v
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data network, then using repeat sim
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CHAPTER 3 kEY fINDINgS Attribution
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to the identification of change in
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Warming from greenhouse gas increas
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3.2.2 Changes in temperature Extrem
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odology has not yet been applied ex
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Figure 3.4 Top two panels: Projecte
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is a major influence; during El Ni
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ut no clear trend in tropical cyclo
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significant trends beginning in the
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3.3 PROjECtEd FUtURE ChANgES IN ExT
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Warm episodes in ocean temperatures
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extreme in daily total precipitatio
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water availability. However, the co
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specifically for hurricanes. The id
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Other studies using comparatively l
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Vecchi and Soden (2007) have assess
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the trend depends on adjustments fo
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tropical cyclone frequencies compar
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CHAPTER 4 BACKGROUNd Weather and Cl
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the existing uncertainties in tropi
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• • • The NOAA Science Adviso
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utable to climate change. However,
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Page 141 and 142:
APPENDIX A Statistical Trend Analys
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Page 145 and 146:
Page 147 and 148:
GLOSSARY AND ACRONYMS GLOSSARy affo
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eforestation the process of establi
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REFERENCES CHAPtER 1 REFERENCES Acu
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Version 5.1 [Online Database]. Univ
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Caribbean: normalized damage and lo
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Bromirski, P.D., D.R. Cayan, and R.
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2005. Geophysical Research Letters,
Page 161 and 162:
ensemble of global coupled model si
Page 163 and 164:
wave spectra under hurricane wind f
Page 165 and 166:
Zhang, R., T.L. Delworth, and I.M.
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in the 2005 Caribbean coral bleachi
Page 169 and 170:
Huntington, T.G., G.A. Hodgkins, an
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Miller, N.L., K.E. Bashford, and E.
Page 173 and 174:
Tonkin, H., G.J. Holland, N. Holbro
Page 175 and 176:
Oouchi, K., J. Yoshimura, H. Yoshim
Page 179 and 180:
Global Change Research Information
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