CE 401Climate Change Science and Engineering

evolution of climatechange since the industrial revolution

9 February 2012

http://www.skepticalscience.com/global-cooling-mid-20th-century-advanced.htm

http://www.hillsdale.edu/news/imprimis/archive/issue.asp?year=2007&month=08

www.realclimate.org

http://solar-center.stanford.edu/sun-on-earth/glob-warm.html

http://hockeyschtick.blogspot.com/2010/09/is-sun-causing-global-warming.html

http://www.pbs.org/wgbh/warming/debate/singer.html

where are we in the syllabus: latest version always on website

the global picture

Global COGlobal CO2 2 distribution in ppmdistribution in ppm

380 parts / million380 parts / million

372 ppm372 ppm

• last decade is the warmest decade on record• increase in past 25 years is ~ 0.2°C/decade• why the leveling off/cooling in the 50’s? – CO2 record

is very smooth – no big bumps and wiggles

NASA Global Temperature Record 1880 - 2008

source: GISS, 2010

NASA Global SURFACE Temperature Record 1880 - 2008

source: GISS, 2010

surface temps are different than temps above the earth surface – where do satellites measure

huge discussions about “where” to measure temp – stratosphere shows a cooling

altitude dependent weighting functions for satellite temp sensitivity

stratosphere

mid troposphere

lower troposphere

actual surface

temperature anomaly vs time 1960 – 2006 as obsv by satellite

What are some of the problems with these graphs of

surface temperature vs time?

There are lots of problems with these graphs!! name some

• where is temperature data collected (geographic distribution)

• how is temperature collected? (same method everywhere?)

• what affects the reading of the thermometer? (surroundings)

• consistency of measurement method over a period of years

urban heat island effect

California surface weather stations

Robinson et al (2007): Surface temperature trends 1940-1996 from 107 measuring stations in 49 CA counties. Trends combined for counties of similar population. The “X” show the stations used by NASA GISS for their estimate of global surface temperatures. original source: F. Singer, Hot Talk, Cold Science, 1997

California weather stations

how would you go about quantifying the urban heat island effect?

where are the urban areas?

where are the urban areas?

source, J Geophys Res.,2003

current locations of global thermometers

NOAA 2010 tied 2005 as the hottest year on record

look at other data sets

sea surface temperature 1850 - 2004

source: IPCC 2007 what are potential problems with this graph?

red = observations

models

red: reconstructed sea level fields since 1870 (Church and White, 2006)blue: coastal tide measurements since 1950 (Holgate/Woodworth 2004)black: satellite altimetry (Leudiette et al, 2004)

sea level change 1880 - 2004

source: IPCC 2007

Figure 5.1

0-700m layer. shading = 90% confidence.

Global ocean heat content

source: IPCC 2007

total column water vapor in %/decade monthly averages 1988 – 2004 over ocean

Snow cover and Arctic sea ice are decreasing (area vs time)

Spring snow cover in millions of square km1920 - present

Arctic sea ice area decreased by 2.7% per decade

1979 - 2005

source: IPCC, 2007

glaciers are retreating

Glaciers and frozen ground are receding

area of seasonally frozen ground in NH has decreasedby 7% from 1901 to 2002

increased Glacier retreat since the early 1990s

source: IPCC 2007

Palmer Drought Severity Index 1900 - 2002

source: IPCC, 2007

observations of measured change – IPCC 2007

detection of significant change is a statistical problem:

• finding a small signal in a sea of poorly understood noise• the instrumental record is short --> rely on proxy measurements• changes have obviously occurred over the past 100 years that are

not human related

• if an observed change in the record is judged unlikely to have occurred due to natural processes --> implicates human factors (???)

• assignment of attribution to a human cause requires considerationand elimination of all plausible non-human mechanisms

• can’t eliminate all plausible mechanisms

• cause and effect are usually approached with a series of controlled experiments, but this cannot be done in this case

• experiment is not systematic - too many parameters are being changed at one time

Global Mean Temperatures

Annual meanSmoothed series5-95 decadal error bars

source: IPCC = source: IPCC = Intergovernmental Panel on Climate Change, 2007Intergovernmental Panel on Climate Change, 2007

11 of the past 12 years are the hottest on record

Hansen et al, 2001 – on class website now

% time during year when temps were below 10th percentile for cold nights or abovethe 90th percentile for warm nights: black 1901-1950, blue 1951-1978, orange 1979-2003