Observed Climate Variability and Change

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Observed Climate Variability and Change

• Jay H. Lawrimore
• NOAAs National Climatic Data Center
• Asheville, North Carolina

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Overview

• Trace Gases
• Temperature
• Sea ice/Snow Cover/Sea Level
• Precipitation/Drought
• Tropical Cyclones/Tornadoes
• New Transportation-related activities

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Trace Gases CO2 and CH4

• CO2 has increased from 280 ppm at start of
  industrial revolution to 380 ppm today
• 2005 global avg 378.9 ppm
• Since 1900, there has been a 22 increase
• Avg annual increase of 1.6 ppm since 1980
• Rate of CH4 increase has slowed in recent years
• Global mean 1774.8 ppb in 2005

CO2 - Mauna Loa
CH4 - Mauna Loa
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Trace Gases N2O and SF6
SF6
N2O

• Present in lower concentrations than CO2
• Radiative forcing per molecule is much greater
• SF6 22,000 more times effective IR absorber
• Total radiative forcings relatively small
• Rapid growth rates and IR absorbing effectiveness
  concern for future
• SF6 5/year increase since 1996
• N2O 0.25/year since 1978

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1000-Year Temperature Record
Jones, PD ME Mann, 2004. Climate Over Past
Millenia. Reviews Of Geophysics 42 (2) Art. No.
RG2002
Temperature reconstruction created from tree
rings, ice cores, ice melt, corals, lengthy
instrumental records.
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New NOAA/NCDC Land Ocean Blend
Global Mean Temperature over Land Ocean
Preliminary New NOAA Surface Temperatures

• Global surface temperature above 1998 record
  without strong El Niño episode
• Continuation of steep warming trend brought
  global temperature to 1998 levels in only 7 years
• 9 of 10 warmest years on record have occurred
  since 1995

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New NOAA/NCDC Land Ocean Blend
Global Mean Temperature over Land Ocean
Preliminary New NOAA Surface Temperatures

• No one year definitively warmest on record
• Sampling, Random and Bias Errors analyzed to
  estimate uncertainty in annual anomalies
• Sampling and Random Errors decrease with time due
  to improved coverage and better instruments and
  measurement techniques

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Global Temperature Change vs CO2 Change
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Global TemperaturesLand, NMAT, SST

• Temperature changes over 20th century are
  extremely consistent across land and oceans
• Both show pronounced warming in 2 phases
• 1915-1945 and 1976-present
• Much stronger warming over land in current period
• Continental warming in mid-latitude Northern
  Hemisphere
• Likely due to atmospheric circulation changes in
  winter half
• Oceanic cooling in S. Hem.
• Possibly due to Pacific Decadal Oscillation AAO

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Annual Temperature Trends
1901 - 2005
1979 - 2005
Deg C/Decade

• Increasing temperatures across most land and
  ocean surfaces
• 1901-2005, warming is global with a few
  exceptions, e.g. Southeast US and N. Atlantic
• 1979-2005, warming largest in mid high
  latitude regions of N.H.
• 1979-2005, portions of southern oceans show
  cooling

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Tropospheric Temperatures1958-2005
1979-2005 RATPAC 0.15C/decade (0.15C) HadAT2
LT 0.16C/decade (0.15C) UAH LT 0.13C/decade
(85N-50S) Decadal trend since 1958
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Global Max and Min Temperature1950-2004

• Minimum temperatures rising faster than maximum
• Overall Trends 1950-present
• Min 0.20C/decade
• Max 0.14C/decade
• Trends 1979-present
• MinMax 0.29C/decade
• Cloud cover Precip trends accounted for 80 of
  variance in DTR in U.S., Australia, mid-Latitude
  Canada, and former Soviet Union

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Affect of Warming on Temperature Extremes

• Warm nights
• Minimum daily temp 90th percentile
• Globally- Annual warm nights increased 25 days
  since 1951
• Largest over Eurasia
• Doubling over N. Africa, N. South Am.

Alexander et al. 2005

• 1951-2003 At least 40 yrs of data required
• 74 of sampled land area showed an increase in
  warm nights

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Affect of Warming on Temperature Extremes

• Warm days
• Maximum daily temp 90th percentile
• Increasing trend not as large as warm nights
• Larger areas of decreasing trends

Alexander et al. 2005

• 1951-2003 At least 40 yrs of data required
• Black lines enclose regions where trends
  significant at 5 level

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Temp and Apparent Temp Trends in US(June-August,
DegC/Decade)
Gaffen and Ross, 1998
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Temperature Summary

• Global mean temperatures increased at a rate of
  0.6 0.7 C/century since 1900
• Much more rapid warming since 1976
• Similar trends on land and oceans
• Temperatures increasing in troposphere
• Minimum temperature rising faster than maximum
  temperature since 1950
• Other effects
• Lengthening the freeze and frost-free seasons in
  many mid- and high-latitude regions
• Widespread decreases in number of days below
  freezing
• Increases in number of warm days and nights

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Arctic Sea IceSnow CoverSea Level Changes
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Arctic Climate

• Arctic-wide annual avg anomalies (60N-90N)
• Large region-to-region differences in 1930s
• More widespread and stretching into mid-latitudes
  in 1990s and beyond

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Arctic Sea Ice Extent March/September

7 Decrease in end-of-summer Arctic sea ice in
past 25 years
March Mean Extent 15.7 Million km2 2005 14.8
Million km2 Sept Mean Extent 6.9 Million km2
2005 5.6 Million km2

• Rate of decrease in March -2/Decade
• In September -7/Decade

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Arctic Sea Ice Extent March/September

March Mean Extent 15.7 Million km2 2005 14.8
Million km2 Sept Mean Extent 6.9 Million km2
2005 5.6 Million km2
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Northern Hemisphere Snow Cover Extent
Courtesy David Robinson, Rutgers Snow Lab
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N. Hem. Spring Snow Cover Extent
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Global Sea Level Changes from Satellite Altimeter
Observations
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Global Sea Level Trends since 1993
Equatorward winds, upwelling, reduced sea level
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Sea Level Rise

• Geographical patterns similar to upper ocean heat
  content change
• Suggests that regional sea level changes are
  largely controlled by thermal processes
• Smaller of total trend is likely due to melting
  of grounded ice on Greenland /or Antarctica
• Trend (2.9 0.4mm/year) is significantly higher
  than 20th century rate of 1.8 0.3 mm from tide
  gauge measurements over past 50-100 yrs
• Is this part of a longer-term trend or just
  decadal variability?

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Ice Sheets

• Vast majority of Sea Level rise was due to
  warming ocean temperatures during 20th century
• Thermal expansion is expected to be biggest
  contributor in 21st century
• BUT..
• Recent research (Rignot and Kanagaratnam, 2006
  Science) has found acceleration in ice discharge
  on the Greenland ice sheet.
• Doubling of ice sheet mass discharge in last
  decade from 90 to 220 cubic kilometers per year.

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Precipitation andExtremes
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Regions where disproportionate changes in heavy
and very heavy precipitation occurred compared to
the mean (first half of 20th century to present)
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Drought/Extreme Wetness in the US
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Drought/Extreme Wetness in the US
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Tropical Cyclones

• Numerous records established in Atlantic Basin
• Most named storms and hurricanes 27 15
• Previous record 21 (1933) 12 (1969)
• Three cat 5 storms (Katrina, Rita, Wilma)
• Previous record of 2 in 1960 and 1961

• 7 named U.S. landfalling storms (Tied 2nd) with
  8th (Ophelia) brushing N.C. coast
• Record 8 landfalling in 1916 and 2004
• Lowest central pressure for Atlantic Hurricane
• Wilma (882 mb) in October. Previous 888 mb
  (Gilbert, 1988)

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Atlantic Tropical Cyclones

• Active season has been attributed to
• Century scale trend in sea surface temperatures
  contributing to anomalous warmth in Atlantic and
  Gulf of Mexico
• Active phase of multi-decadal oscillation

• Recent research points to link between warming
  ocean temperatures and frequency of strongest
  tropical cyclones --- BUT

Jul-Sep SSTs in Gulf of Mexico
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Global Tropical Cyclone Activity

• ACE Index
• Sum of Squared 6-hourly wind speeds
• Difficult to look beyond 1980 on a global basis
• Lack of data in basins such as N. and S. Indian
  and S. Pacific

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Very Strong to Violent Tornadoes

• A relatively quiet year in 2005
• Only Nine F3-F5 tornadoes during March-August
• Decreasing trend since 1970s
• November a very active month

Wind speeds in excess of 158 mph

• 23 fatalities in Evansville, IN on 6th Indianas
  deadliest tornado since 1974 Super Outbreak
• More than 30 tornadoes in 6 states on 15th

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Storm Losses
Eastlering et al. 2000, Science
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Billion Disasters in the US

• Inflation adjusted costs due to weather-related
  extremes continue to rise
• Record damages in 2005
• Greatest number of billion-dollar disasters in
  the southern and southeastern U.S. since 1980

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Precipitation Extremes Summary

• Increase in heavy precipitation events
• Increase in losses in US during past 50 years
  largely due to societal shifts
• Future climate change leading to more extreme
  events will exacerbate the problem
• Some signs of long-term changes in tropical storm
  intensity but evidence not conclusive
• Little compelling evidence for widespread
  systematic long-term changes in severe local
  weather (tornadoes, thunder days, lightning and
  hail)

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Conclusions

• Temperatures over past 100 years have warmed
• Greatest warming in high latitudes.
• Decrease in Arctic Sea Ice.
• Decrease in NH snow cover
• More warming in minimum (nighttime) temperature.
• Observed Sea level rise.
• Large-scale precipitation over land has
  increased.
• Increase in high latitudes, decrease in Tropics.
• Evidence for increases in heavy precipitation
  events.
• No conclusive evidence of increase in hurricanes
  or tornadoes.
• Uncertainties due to observing system issues,
  etc. but taken together balance of evidence
  points to discernable human influence on the
  climate.

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Future Transportation-related Activities at NCDC

• Archiving/Use of Roadway Weather Information
  System (RWIS) data
• Development of Evacuation Climatologies

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• NHTSA reports over 40,000 fatalities associated
  with automobile accidents per year.
• NCDC receives a significant number of requests
  for weather data at or near accident sites
• State DOTs use NCDC archives
• Reduce settlement claims
• Retrospective analysis of event
• Immediate benefits are foreseen in archiving
  highway weather and road condition.
• Blending satellite, radar, and surface data
  including highway weather reports will create
  more compelling products
• Climatologies of fog, snow, weather
• By time-of-day, location
• Compare city commuting- hour weather

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Developing a Hazard Resilient Community
Evacuation Climatologies for Strategic Planning

• Proposed by a Western North Carolina community
  leaders association
• Problem How best to protect citizens from
  hazardous weather extremes
• Location dependent
• No single solution will work for all communities
• Engineering and design based on the most
  up-to-date climate statistics

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Developing a Hazard Resilient Community
Evacuation Climatologies for Strategic Planning

• Climate is used as the basis of long-range
  planning operations associated with hazard
  mitigation and public safety
• In what communities is it safe to establish
  evacuation shelters
• Are existing evacuation shelters structurally
  sound to withstand conditions under a changing
  climate
• Are evacuation routes which were planned decades
  ago safe under storm surge scenarios likely to
  occur in todays climate
• How will the climate of today and tomorrow affect
  the design of innovative evacuation plans such as
  the use of railway systems to evacuate the local
  populace

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THE END