Transcript General - Geological Society of America

Geologic evidence
of recurring
climate cycles and
their implications
for the cause of
global warming
and climate
changes in the
coming century
Don J.
Easterbrook

 Is
Geologic issues about
global climatic warming
global warming real?
 What is the evidence for CO2 as the cause of
global warming?
 What is the geologic evidence for natural
cycles as the cause of global warming?
Some Geologic Facts

Global climate warmed ~0.6°
C from 1910 to ~1940.

Global climate cooled ~0.5° C
from ~1940 to 1977

Global climate warmed ~0.5°
C from 1977 to 2000.

Global climate cooled ~0.3° C
between ~1880 to ~1910
and was ~0.9° C cooler in
1890 than 2000
The
global climate has been
warming since the Little
Ice Age (~400 years).
Evidence that CO2 is the cause of global warming


CO2 and global temperature have both risen
over the past 30 years.
Computer models can be adjusted to show
temperatures parallel to global
temperatures.
Composition of the atmosphere
CO2 now makes up
0.038% of air
Before human input,
CO2 was 0.028% to
0.030%
Human input has
raised CO2 by
0.008%
Facts:
1. Half of the warming in the past century
occurred before CO2 began to rise
sharply.
2. For 30 years after CO2 began to soar,
global cooling occurred, rather than
warming.
3. Of the many global warmings and coolings,
only the last one (the past 30 years)
corresponds to rising CO2.
~80% of CO2 emissions have occurred since 1945
Greenland warming has followed the global pattern
Past climate changes
 “Our civilization has never experienced any environmental
shift remotely similar to this. Today’s climate pattern has
existed throughout the entire history of human
civilization.” (Gore, 2006)

“Temperature has spiked within the past few years unlike
any previous temperature spike in history.” (Mote, 2007)

“Current warming is 10 times greater than ever before seen
in the geologic record. The chance that warming is natural is
less than 10 percent..” (Newsweek, August 13, 2007)
10 episodes of global warming/cooling in the past 15,000 yrs
What the data shows

Global temperatures have risen 1° F in the last
century.

Temperatures in Greenland changed abruptly at
least 9 times in the late Pleistocene.




Temperature changes of 18-23° F/100 yrs
occurred 3 times.
Temperature changes of 13-14° F/100 yrs
occurred 3 times.
Temperature changes of 5-7° F/100 yrs occurred
4 times.
None of these temperature changes could have
been caused by manmade CO2 emissions.
Holocene climate changes
Rapid cooling and warming at 8200 yrs. B.P.
Medieval Warm Period

The Medieval Warm Period was a time of warm climate ~900–1300 AD.

Grain crops flourished in Europe.

The population more than doubled and many new cities arose.

The Vikings took advantage of the warm climatic to colonize Greenland.

Wine grapes were grown as far north as Britain.

Prolonged droughts affected the southwestern U.S.

Western North America warmed, glaciers receded.

An eastern Antarctic Peninsula ice core shows warmer temperatures

Sediments in Lake Nakatsuna in Japan record warmer temperatures.

Sea surface temperatures in the Sargasso Sea were approximately 1°C
warmer than today.

Equatorial east Africa was drier from 1000-1270 AD.

The Medieval Warm Period appears to have been a global event.
LITTLE ICE AGE
 ~1300
 Much
AD, temp. dropped ~4° C (7° F ) in ~20 yrs
colder and wetter, ~4° C cooler than present
 Violent
storms, early snow, flooding
 Glaciers
advanced all over the world.
 Massive
crop failures in Europe--large population
decline in Europe; ~1.5 million people died;
 Wine
production dropped sharply
 Themes
River in London froze over
Solar irradiance, sunspots, and glaciers
Boulder Glacier, Mt. Baker
1940 to 1956
1956 to 1979
Easton Glacier, Mt. Baker
1940 to 1956
1956 to 1979
Comparison of glacial activity and ocean temperatures
Facts About Global Climate Change
Over the Past Century and Millennia




Evidence for recurring cycles of global climate change over the past
centuries and millennia clearly show many natural climatic warming
and cooling events, long before CO2 emissions raised atmospheric
CO2 levels.
Greenland ice core isotope and temperature data show 10 periods of
climatic warming far greater than recent warming (up to 20 times
greater per century). Glacier fluctuations and ice core data show a
repeating pattern of warm/cool episodes in the past 500 years and
we are right on schedule with two cooling periods and two warming
periods this century. All of the global warming in the past 500
years can be explained by these natural climatic cycles.
Past climate changes follow cyclic 25-35 year patterns that can be
traced for the past 400–1000 years in Greenland ice cores, glacier
fluctuations, and historic observations.
The Earth is now near the end of a 30–year warm cycle, fitting the
pattern of comparable cycles over the past 200 years.



The current warm cycle coincidently corresponds to high
atmospheric CO2 levels. However, the preceding 30–year
global cooling cycle (1945-1977) occurred despite the
dramatic rise in CO2 emissions that began about 1945).
About half of the global warming of the past century
occurred before 1945, so increased atmospheric CO2
clearly did not control global climate changes then. The
abrupt shift in 1977 from the 1945-1977 cool period to
the 1977-2007 warm period was not reflected by any
significant change in CO2.
The only physical evidence for CO2 causing global warming
is that warming and CO2 have both risen for the past 30
years. After CO2 began to soar in 1945, global cooling
occurred for 30 years, rather than warming.
CO2 began to rise sharply in 1945, but global
temperatures declined for 30 years
Solar effects and climate change
Global climate changes
correlate well with
changes in:
1. Solar irradiance.
2. Numbers of sunspots.
3. Production of 10Be and
14C in the atmosphere
from radiation.
Few sunspots during the Little Ice Age
Global temperature change and sunspots
Solar irradiance and global warming
 25-30
yr. global warming/cooling phases that occurred
during the past century coincided with changes in
solar irradiance.
 Global
climate changes in the geologic past have
coincided with changes in production rates of 14C
and 10Be.
Where are we
headed during
the coming
century?
ICPP predictions
Global temperatures
will increase as much
as 10° F by 2100
Predicted global temperature changes this century
Predicted global temperature changes this century


The IPCC predicts that global temperature will rise 1° F
(above present temp) by 2011, whereas the pattern of
natural warm/cool cycles predicts slight cooling. The
difference is so large, that in only 3 years we should know
which direction we’re heading.
The predicted IPCC temperature increase by 2011 is 1° F
greater than that predicted by extrapolation of past
climatic cycles and nearly 2° F greater by 2030. These
differences are greater than warming of the entire past
century, so should be easily detectible. Thus, the next few
years may tell us whether we're heading for the global
catastrophe predicted by IPCC or minor warming
predicted by climate cycles.
What lies ahead in this century?
 Two
choices:
 If
past climate cycles persist and climate
cools in the next 30 years (rather than
soaring), the IPCC will have been the
greatest scientific boondoggle in the
history of science.
 If
IPCC predictions are correct, we’re
headed for the greatest global
catastrophe since the Little Ice Age.