The Pliocene Warm Interval: Is It An Analogue For Future Warming?

1
The Pliocene Warm Interval Is It An Analogue
For Future Warming?
Abstract The Pliocene Epoch (5.3 to 2.6 Ma) is
the last great global warming before the
beginning of the Pleistocene ice age.
Paleoclimate proxy data, such as animal and plant
fossils on land or in the ocean, suggest that
the Earth was 2 to 3 degrees C warmer than
present, with the most pronounced heating found
in the polar regions. There may also have been a
persistent El Niño-like feature, called El Padre,
that led to increased warmth of tropical ocean
surface waters. Despite these differences, the
concentration of atmospheric CO2 during the
Pliocene was similar to current day levels (380
40 ppm). For this reason, climate researchers
want to understand whether the Pliocene
represents a warm world in an equilibrium state,
a condition that we may eventually achieve in the
near future even if CO2 emissions are stabilized.
For our study, we used EdGCM/GISS GCM Model II to
explore whether an El Padre could have
contributed to the Pliocene global warming. We
have also examined to what extent we can draw
parallels between the regional climate impacts of
an El Padre-driven Pliocene climate, and a strong
modern El Niño, such as the 1997/1998 event,
which has been projected to become a persistent
feature of a future warm climate. We find that an
El Padre/persistent El Niño could have played an
important warming role for the Pliocene, and
therefore has implications for our future
climate.

• Objectives
• To determine if the Pliocene is a proper analog
  towards the future climate changes that have been
  projected by scientists.
• Compare and contrast the characteristics of the
  Pliocene warm climate and possible forcings, such
  as the El Padre (persistent El Nino) effect, to
  our own modern day climate characteristics.

• Results
• In the predicted SST runs, we saw a greater
  increase in higher latitude temperatures when
  compared with the modern control run, consistent
  with
• Pliocene paleoclimate proxy data.
• Our most extreme pSST run (425 ppm CO2) had a
  global average temperature increase of 2 degrees
  Celsius compared to our modern control run. The
  polar regions showed a temperature increase of up
  to 29 degrees Celsius. However, the
  mid-latitudes went through more warming in the
  northern hemisphere than in the southern
  hemisphere, most likely due to the distribution
  of land vs. ocean in the northern hemisphere vs.
  the southern hemisphere.
• The equatorial regions did not change
  significantly in terms of temperature, with some
  areas even cooling (not by more than 1 degree
  Celsius).
• Global average precipitation is only slightly
  higher than that of the modern control run
  however, many places undergo drastic increase or
  decreases.
• For example Central America, the Atlantic ocean,
  and the Asia-Pacific islands get significantly
  dryer than they are today (up to more than 3
  mm/day less), whereas other places, such as
  Africa, South America, and the western Pacific
  ocean get a lot wetter (up to 2.5 mm/day).
• In the El Padre predicted SST runs, we saw a
  much warmer climate (gt 3
• degrees Celsius) than the modern control run
  however, the maximum
• temperatures (present in Antarctica) remained the
  same as they did in the normal pSST runs.
  Surface air temperature-wise the El Padre runs
  simply showed more pronounced warming in the
  areas that where undergoing warming in the pSST
• runs.
• Precipitation patterns in these runs do bare
  similarities to those
• regional patterns expected from Pliocene
  paleoclimate proxy data as
• well as with strong modern El Nino events. For
  example, we see a
• significant increase in precipitation in the
  equatorial west coast of South America, more
  precipitation in the Indian subcontinent (keep in
  mind there are also areas of decreased
  precipitation in the Indian subcontinent),
• decrease around the Japanese islands and a few
  areas of increased precipitation in Africa.

• Importance of This Study
• Understanding the factors and forcings that
  produced the Pliocenes warm stable climate can
  help us understand what our world may become like
  in the near future, even if the CO2 emissions are
  stabilized at or near current levels.

This is an anomaly map of our Pliocene control
run minus out modern control run, showing us
how different the Pliocenes climate was from our
own despite the similar forcings.
Pliocene/ El Nino like Regional Impacts- this is
a map of the temperature and precipitation
during the Pliocene which is very similar to El
Nino. What we think is that during the Pliocene
there was a permanent El Nino. To differentiate
the two we call this El Padre.

• Methods
• We used a software called EdGCM, which utilizes
  the NASA/GISS GCM Model II, to run all our
  climate simulations.
• We first ran a series of sensitivity experiments
  using specified sea surface temperatures (SSTs)
  to examine the models response to certain
  forcings, such as greenhouse gas level changes.
• We then ran a series of predicted SST
  experiments, in which the models ocean was
  allowed to respond to climate forcings set for
  each simulation.
• We ran a total of four ensembles of runs, two
  with specified SSTs and two with predicted SSTs.
  For each ensemble, we changed the CO2
  concentration in 5 ppm increments, from 380 ppm
  to 425 ppm. To one specified and one predicted
  SST ensemble, we also added the El Padre
  phenomenon by increasing tropical SSTs between
  16N-16S.

Pliocene El Padre Time Series
Pliocene Time Series without El Padre
Conclusions Our findings to date do suggest that
an El Padre phenomenon, or persistent El Nino,
did contribute to a global average increase in
temperature during the Pliocene. Regional
patterns of temperature and precipitation are
also reasonably well reproduced by our Pliocene
El Padre simulations although some differences
remain. If the Pliocene does in fact represent a
warm climate at equilibrium, it is very likely to
be a good analog for our future warm world once
our climate is no longer in transition.
Sponsors National Aeronautics and Space
Administration (NASA) NASA Goddard Space Flight
Center (GSFC) NASA Goddard Institute for Space
Studies (GISS) NASA New York City Research
Initiative (NYCRI) Contributors Principal
Investigator 1 Dr. Mark Chandler Principal
Investigator 2 Dr. Linda Sohl Graduate Student
Sonali Shukla High School Teacher Mohamed
Shanap Undergraduate Student Carimaxy Benitez
NYCRI Apprentice Francisco Benavides
Surface Air Temperature- This map illustrates the
similarities that the Pliocene/El Nino regional
impact and our Pliocene maximum run minus our
Pliocene control run.
Precipitation- The arrows indicate where most of
the precipitation is taking place, very similar
to the regional precipitation shown above. This
map is a Pliocene to its maximum 425 ppm
minus our Pliocene control run 380 ppm.
References Fedorov, A.V,
Dekens, P.S, McCarthy, M, Ravelo, A.C, DeMenocal,
P.B, Barreiro, M, Pacanowski, R.C, and
Philander, S.G, 2006. The Pliocene Paradox
(Mechanisms for a Permanent El Nino) Science,
v.312, p.1485-1489, DOI 10.1126/science.1122666.
Molnar, P, and Cane, M.A, 2007. Early Pliocene
(pre-Ice Age) El Nino-like Global Climate
Which El Nino? Geosphere v.3, p.337-365,
DOI10.1130/ges00103.1.