CE 401

Climate Change Science and Engineering

climate change since the industrial revolution

8 February 2011

HW 6 due Thursday – please submit electronically to rgrivicke@gmail.com AND gmount@wsu.edu --- You work at a consulting firm, and your boss is trying to figure out climate change for part of a presentation to a client. A friend gives him the Robinson article and he passes it on to you (who had CE 401) for critical comment so he is aware of what is reasonable in that article and what is not reasonable. Your job is to provide that critical review.

Note: exam #1 date will be 24 February; topic/team proposal date will be 22 February

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

submit electronically

Science magazine, 7 Feb 2011

• 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 Surface Temperature Record 1880 - 2008

source: GISS, 2010

During the 1950s and 1960s, average global temperatures leveled off, as increases in aerosols from fossil fuels and other sources cooled the planet.

I put the IPCC technical summary, frequently asked questions/answers, andthe chapters on historical climate and observations of temp onto the class website

IPCC 2007

NASA Global SURFACE Temperature Record 1880 - 2008

source: GISS, 2010

surface temps are different than temps above the earth surface

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. Suchselections make the NASA GISS modeled temperatures too high. – cheap shot!!!!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?

Hansen et al, 2001 – on class website now

source, J Geophys Res.,2003

current locations of global thermometers

NOAA (12 JAN 2011) 2010 tied 2005 as the hottest year on record

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

% 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

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

POLICY MAKERS ARE INTERESTED IN THEFUTURE

What will happen and what is the cause?

Models are used to predict future climate

How well do these models predict the past?

Can we trust models to predict the future?

Decisions are based on the models!

source: IPCC 2007 The Climate System - very complicated

What Goes into Atmospheric Climate Models

• mathematical equations to describe air motion and processes• solar flux and its changes in time - Earth energy balance• clouds - largest source of uncertainty in the models

• 61% of the globe on average is covered with clouds• clouds both reflect energy (cooling) - feedbacks• and serve as thermal blankets (warming) - feedbacks

• Earth reflectivity (land, sea/water, ice, snow, vegetation, etc.)• thermodynamics of water and radiation• chemistry and carbon cycle (atmosphere, oceans, biosphere)

• anthropogenic contributions (e.g. CO2 increases with time,

biomass burning, land use changes, etc.)• aerosols which cool the atmosphere (natural and anthropogenic)

The atmospheric models must be coupled to:

• cryosphere• biosphere• oceans• hydrosphere

• all on a high resolution global spatial grid of latitude and longitude and altitude as a function of time and incorporating the many feedback mechanisms that control atmospheric processes

This is a huge job that requires experts from many fields and a large computer! There are a number of groups around the world working on this problem.