Title: 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
1Geologic evidence of recurring climate cycles and
their implications for the cause of global
warming and climate changes in the coming
centuryDon J. Easterbrook
2- Geologic issues about
- global climatic warming
- Is 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?
3Some 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).
4Evidence 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.
5Composition 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
6- Facts
- 1. Half of the warming in the past century
occurred before CO2 began to rise sharply. - For 30 years after CO2 began to soar, global
cooling occurred, rather than warming. - Of the many global warmings and coolings, only
the last one (the past 30 years) corresponds to
rising CO2. - .
780 of CO2 emissions have occurred since 1945
8(No Transcript)
9Greenland warming has followed the global pattern
10(No Transcript)
11Past climate changes
- Our civilization has never experienced any
environmental shift remotely similar to this.
Todays 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) -
1210 episodes of global warming/cooling in the past
15,000 yrs
13(No Transcript)
14What 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.
15Holocene climate changes
16Rapid cooling and warming at 8200 yrs. B.P.
17(No Transcript)
18(No Transcript)
19(No Transcript)
20Medieval Warm Period
- The Medieval Warm Period was a time of warm
climate 9001300 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 1C warmer than today. - Equatorial east Africa was drier from 1000-1270
AD. - The Medieval Warm Period appears to have been a
global event.
21(No Transcript)
22LITTLE ICE AGE
- 1300 AD, temp. dropped 4 C (7 F ) in 20 yrs
- Much 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
23Solar irradiance, sunspots, and glaciers
24(No Transcript)
25(No Transcript)
26Boulder Glacier, Mt. Baker
1956 to 1979
1940 to 1956
27(No Transcript)
28Easton Glacier, Mt. Baker
1940 to 1956
1956 to 1979
29Comparison of glacial activity and ocean
temperatures
30(No Transcript)
31Facts 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 4001000
years in Greenland ice cores, glacier
fluctuations, and historic observations. - The Earth is now near the end of a 30year warm
cycle, fitting the pattern of comparable cycles
over the past 200 years.
32- The current warm cycle coincidently corresponds
to high atmospheric CO2 levels. However, the
preceding 30year 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.
33(No Transcript)
34(No Transcript)
35CO2 began to rise sharply in 1945, but global
temperatures declined for 30 years
36- Global climate changes correlate well with
changes in - Solar irradiance.
- Numbers of sunspots.
- Production of 10Be and 14C in the atmosphere
from radiation.
37Few sunspots during the Little Ice Age
38Global temperature change and sunspots
39Solar 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.
40Where are we headed during the coming century?
41ICPP predictions Global temperatures will
increase as much as 10 F by 2100
42Predicted global temperature changes this century
43Predicted global temperature changes this century
44- 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
were 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.
45What 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, were headed for
the greatest global catastrophe since the Little
Ice Age.