1. How has the climate changed during the very recent past?

2. What can we say about current climate change?

3. How do climate models work and what are their predictions for the future?

What we wish to learn Today:

Possible Causes of Climate ChangePossible Causes of Climate Change

Power: 4 x 1026 W 2 x 1017 W

Long-Term 1. Solar Luminosity2. Shifting Continents3. Greenhouse gases

Medium-Term 1. Orbital parameters2. Greenhouse gases

Short-Term 1. Oceans2. Sunspots3. Volcanoes 4. Greenhouse

gases

In May, 2010, the National Academies of Science reported to Congress that “the U.S. should act now to reduce greenhouse gas emissions and develop a national strategy to adapt to the inevitable impacts of climate change” because global warming is “caused largely by human activities, and poses significant risks for — and in many cases is already affecting — a broad range of human and natural systems.”

Rep. John Boozman (Arkansas): “Is man causing it, or, you know, is this a cycle that happens throughout the years, throughout the ages. And you can look back some of the previous times when there was no industrialization, you had these different ages, ice ages, and things warming and things. That’s the question.” [KTHV Little Rock, 3/10]

Rep. Roy Blunt (Missouri): “There isn’t any real science to say we are altering the climate path of the earth.” [Human Events, 4/29/09]

Sen. Tom Coburn (Oklahoma): “I am not the smartest man in the world … But I have been trained to read scientific documents, and it’s malarkey.” [Sooner Tea Party, 8/25/09]

Ron Johnson (Wisconsin): “I absolutely do not believe that the science of man-caused climate change is proven. Not by any stretch of the imagination. It’s far more likely that it’s just sunspot activity, or something just in the geologic eons of time where we have changes in the climate.” [Milwaukee Journal-Sentinel, 8/19/10]

John Raese (W. Virginia): “And if you have one volcano in the world that one volcano puts out more carbon dioxide than everything that man puts out.” [Charleston Gazette, 7/22/10]

The threat to our society from failure to recognize, slow down, and adapt to climate change is just one facet of the subset of threats that we face from the denial of science, the rise of opinions over facts, and the forced restraint of our ability and freedom to develop and use our minds.Rep. Paul Broun (Georgia): "All that stuff I was taught about evolution and embryology and the Big Bang Theory, all that is lies straight from the pit of Hell“. "You see, there are a lot of scientific data that I've found out as a scientist that actually show that this is really a young Earth… about 9,000 years old.“ Broun is on the House Congressional Science Committee.[6 October 2012, and captured on video at a Sportsmans Banquet, September 2012 – video http://www.youtube.com/watch?v=Ge64kMFoQEo ]

Neil Newhouse, political pollster, “We’re not going to let our campaign be dictated by fact checkers.” [NY Times, Kevin M. Kruse, published 5 Nov 2012]

2012 Texas Party platform opposes “the teaching of … critical thinking skills and similar programs that … have the purpose of challenging the student's fixed beliefs and undermining parental authority.”[NY Times, Kevin M. Kruse, published 5 Nov 2012]

North Carolina's Senate legislation (HB 819) that would have required the state's Coastal Resources Commission to base predictions of future sea level rise along the state's coast on a steady, linear rate of increase. {That is, to deliberately ignore the science indicating that sea-level rise has been and will be non-linear, rising more quickly over time as ice sheets melt}[Science Insider, by Jane J. Lee on 3 July 2012, http://news.sciencemag.org/scienceinsider/2012/07/update-revised-north-carolina-se.html ]

Recent Trends in

TemperatureN.H

. T

em

pera

ture

(°

C)

1000 14001200 1600 1800 2000

0

1

-1

2

Year

N.H

. T

em

pera

ture

(°

C)

1000 14001200 1600 1800 2000

0

1

-1

2

Year

Dep

art

ure

s in

tem

p

(deg

C)

from

1961-1

990 m

ean

Global Temperature

Data from thermometers

Year

Solar Activity and Solar Activity and ClimateClimate

Very few sunspots seen between 1645 and 1715

Corresponds to the time of the “Little Ace Age”

Sunspot number

Little Ice Age

http://solarscience.msfc.nasa.gov/SunspotCycle.shtml

Sunspot Number

0

50

100

150

200

250

1750 1800 1850 1900 1950 2000Year

Nu

mb

er o

f Su

nsp

ots

Year

Nu

mb

er

of

sun

spots

Sunspot number

Sunspots increased at the same time

that global temperatures

increased

Multicollinearity!

Change in sunspot number is greater

than change in solar radiation. The change in solar radiation is only

about 0.1%, too small to account for the full temperature increase

Sunspots, solar

radiation, and

temperatureGlobal Surface Temperature 1978-2009

Pre-1991

Post-1991

VO

LCANO

!Ash on cars

Volcanic eruptions cool global temperature

Volcanoes spew out ~160x less CO2 than humans do…

Satellite troposphere temperature data

El Niño index

El Niño effect on temperature

Satellite data minus El Niño effect

Volcano effect on temperature

After removing El Niño and volcanoes

Residual Trend: 0.11°C per decade

Effects of El Niño and volcanoes on air temperatures

Pinatubo

’97-98 El Niño

Summary of Climate Forcingsin “energy” terms of Watts per

m2

Orbital variations ~ 0.5 W m-2 / century (occurs over long time scales)

Solar variation ~ 0.29 W m-2 peak-to-peak over ~2 centuries

Greenhouse Gases - past: ~ +0.0067 W m-2 / century CO2, 4050 BC to ~1000

AD ~ +0.0016 W m-2 / century CH4, 4050 BC to ~ 1500

AD ~ +0.0006 W m-2 / century N2O, 4050 BC to ~ 1000

BC

Volcanic eruptions 0 down to -10 W m-2, but short lived (a few years).

Estimated long-term mean forcing ~ -0.3 W m-2

* Current GHG emission – Doubling of CO2 ~ 4 W m-2 !

Past and Modern Changes on Earth – CO2, CH4, and temperature are

correlatedCO2

CH4

Temp.

Atmospheric CO2 concentration and temperature are correlated in the Vostok ice core

Temperature variations (ºC)

Atm

osp

heri

c C

O2 c

on

cen

trati

on

(p

pm

)

Glaciations

Deglaciatio

ns

Modern

Paleoclimate provides perspective on where we are headed …

IPCC Projectionsto 2100

1000 1200 1400 1600 1800 2000

0

0.5

1

-0.5

2

4

3

5

6

1

0

N.H

. Tem

pera

ture

(°

C)

Global Temperatur

e (°C)

Types of Models:Physical Models (a desktop globe)

Statistical Models (a regression, y=mx+b)

Conceptual Models (a flow chart)

Computer Models (Global Climate Models, GCMs)

“Climate models are only sophisticated tools, not crystal balls”

“A useful model is not the one which is true, but the one that is informative”

“ …all models are wrong, some are useful”

USING MODELS TO PREDICT CLIMATE

What goes into a climate model?

Climate models work pretty well…

Rainfall [annual]

Which is observed and which is modeled ?

… but there is some

variation

Prediction of the 1997-1998 El

Nino by 6 different GCM

models shows a similar pattern

of climate changes

Models show that anthropogenic causes of temperature change explain what has already

occurred.

Courtesy W. Washington/NCAR

“Climate change” is more than an environmental issue, and is related to

adaptation and societal choices

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC)

The models must use “scenarios” of future GHG

emissions World CO2 emissions

Gig

ato

ns o

f C

arb

on

There are many different “storylines”,

or scenarios of how much CO2 will be emitted by society in

the future

Pick your future…

Source: IPCC TAR 2001

Predictions of large climate changes even by the 2050s

Hadley Centre for Climate Prediction and Research

But, we control our destiny -- Temperature from the present day to the 2080s

Hadley Centre for Climate Prediction and Research

cUnmitigated Emissions

c

c Stabilization of CO2 at 550 ppm

Stabilization of CO2 at 750 ppm

Take Home Message:

Prediction into the future is difficult, but necessary…

Summary

1. Recent changes in Earth's paleoclimate record are likely due to shifts in ocean circulation, and the effects of greenhouse gas increases.  Volcanoes have had only a small effect, and the sun spot record cannot account for the heat input needed.

2. Temperature changes and greenhouse gas abundances are correlated. Rapid global warming is underway and models have been developed to predict the effects of these changes.

3. Global Climate Models (GCMs) are sophisticated tools that predict a much altered climate on Earth during the next century.