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The Diurnal Temperature Range and its Recent Evolution

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... (1950 - 2004) 1950 2004 1979 - 2004 Global Trends (1979 2004) Why? What Affects DTR? Urban Heat Island (increase minimums) ... – PowerPoint PPT presentation

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Title: The Diurnal Temperature Range and its Recent Evolution


1
The Diurnal Temperature Range and its Recent
Evolution
  • Brian Olsen
  • April 20, 2006

2
Outline
  • Introduction to DTR
  • Local Examples
  • Global Trends
  • What affects DTR?
  • Conclusions

3
The Global Warming Signal
Multi-decadal pause in warming
IPCC, 2001
4
Diurnal Temperature Range (DTR)
  • DTR High - Low
  • High Temperature 81F
  • Low Temperature 58 F
  • DTR 81 F 58 F 23 F

Lowest in winter
Highest in summer
SLC WFO
5
KSLC Trends
Warming?
Definite Warming!
E. Crossman
  • But why?
  • What about a nearby rural location?

6
KENV Monthly Mean of Daily Tmax, Tmin, and DTR
(1913-2004)
General loss of warm colors in summer
Missing data
General gain of cool colors in winter
B. Olsen
7
KENV Trends
  • Tmax actually decreases
  • Tmin increases
  • DTR decreases

But where did the trend go?
  • Obviously, this is a complicated problem

Pause in warming
B. Olsen
8
Global Trends(1950 - 2004)
StrongWarming
Steady
StrongWarming
Warming
Decreasing
Steady
Vose et al. 2005
Vose et al. 2005
9
1950 2004 1979 - 2004
GreatestWarming
GreatestWarming
Vose et al. 2005
10
Global Trends(1979 2004)
Trendless
Vose et al. 2005
Vose et al. 2005
11
Why? What Affects DTR?
  • Urban Heat Island (increase minimums) local
    effect
  • Irrigation Desertification not globally
    significant local effect
  • Climate variables
  • Cloud coverage and altitudeexplain 40 of
    variance
  • All vars 55 of variance
  • Other considerations
  • Jet Contrails (Travis et al. 2004)
  • Tropospheric aerosol
  • GHG emissions

Karl et al. 1993
12
Conclusions
  • The planet is warming
  • The planet is getting less cool
  • Historically, minimum temps increased more than
    maximum temps gt decrease in DTR
  • Winter / Spring warmed the most
  • Rate of warming has increased since 1980
  • Recently, minimum temps and maximum temps rise in
    step gt no trend in DTR
  • Winter continues to become more mild
  • Signal most apparent in Northern Hemisphere
  • Cloud cover is significant

13
(In)Conclusions
  • DTR trend is difficult to measure
  • difference between two large quantities
  • Noisy / lots of temporal variability
  • Wide regional variation
  • Global generalizations may be a poor measure
  • Local effects may overpower global trend
  • Model / Observation discrepancy

14
Thanks!
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