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--- pmip3:cmip6:design:plio:index [2015/03/24 10:14] – created jypeter
+++ pmip3:cmip6:design:plio:index [2025/05/15 17:38] (current) – jypeter
@@ Line 1: / Line 1: @@
-~~DISCUSSION~~
 ====== PMIP-CMIP6 Experimental Design Discussion: Pliocene ======
+<note warning>The PMIP4 experimental design available on the PMIP3 wiki has been **superseded** by the experimental design detailed on the [[https://pmip4.lsce.ipsl.fr/doku.php/exp_design|PMIP4 web site]]</note>
 <note tip>\\ Please submit your comments in the Discussion section at the end of this page</note>
+===== Brief overview =====
+The Pliocene epoch was the last time in Earth history when atmospheric CO2 concentrations
+approached modern values (~400 ppmv) whilst at the same time retaining a near modern
+continental configuration. The IPCC 5th Assessment report chapter 5 (Masson-Delmotte et al.,
+) states that that model–data comparisons for the Pliocene provide high confidence that
+mean surface temperature was warmer than pre-industrial (Dowsett et al., 2012; Haywood et al.,
+). Global mean sea surface temperatures have been estimated to be +1.7°C above the 1901–
+mean based on large data syntheses (Lunt et al., 2010; Dowsett et al., 2012). Exiting
+climate model simulations have produced a range of global mean surface air temperature of
++1.9°C and +3.6°C relative to the 1901–1920 mean (Haywood et al., 2013). Model simulations
+have indicated that meridional temperature gradients were reduced (due to high latitude
+warming), which has significant implications for the stability of polar ice sheets and sea level in
+the future (e.g. Miller et al. 2012). Compilations of vegetation (Salzmann et al., 2008) have
+indicated that the global extent of arid deserts decreased and boreal forests replaced tundra, and
+climate models predict an enhanced hydrological cycle, but with a large inter-model spread
+(Haywood et al., 2013). The East Asian Summer Monsoon, as well as other monsoon systems,
+may also have been enhanced (Zhang et al. 2013). Although climate model simulations for the
+Pliocene were assessed in the AR5, these simulations were not derived from the same
+model/same resolution as the CMIP5 future projections, thus reducing the communities’ ability
+to assess and compare changes in global and regional Pliocene climates, vis-à-vis similar
+predictions of future climate change (Haywood et al., 2013).
+We propose a CMIP6 time-slice experiment for the Pliocene to understand the long term
+response of the Earth’s climate system to a near modern concentration of atmospheric CO2
+(longer term climate sensitivity or Earth System Sensitivity), and to understand the response of
+ocean circulation, Arctic sea-ice, modes of climate variability (e.g. ENSO), as well as the global
+response in the hydrological cycle and regional changes in monsoon systems. A Pliocene
+simulation will be of high societal relevance because of its potential to inform policy makers on
+required emission reduction scenarios designed to prevent global annual mean temperatures
+increase by more than 2 to 3 °C in the long term (beyond 2100 AD).
+The proposed CMIP6 simulation for the Pliocene is relevant to two of the WCRP Grand
+Challenges. This includes Clouds, Circulation and Climate Sensitivity because of the enhanced
+CO2 forcing (contemporaneous with modern CO2 forcing), providing a unique opportunity to
+examine an equilibrium climate state to a near modern concentration of atmospheric CO2. The
+pattern of polar amplification preserved Pliocene climate archives can be compared directly with
+the latest generation of CMIP models making a valuable contribution towards addressing the
+potential polar amplification problem. Through the analysis of Pliocene polar amplification in
+CMIP models, and examining the geological interpretation of a seasonally sea-ice free Arctic
+Ocean during the Pliocene, our CMIP6 simulation will also address the WCRP Grand Challenge
+of Changes in the Cryosphere. Whilst uncertainty exists in Pliocene sea level reconstruction, IPCC AR5 states with high confidence that Pliocene sea-levels were higher than the preindustrial
+era, with a number of independent methods indicating a sea-level rise of between 10
+and 20 m. This indicates potential long term instability of both the Greenland and Antarctic Ice
+Sheets (Miller et al. 2012) with CO2 concentrations at approximately 400 ppmv.
+CMIP6 Pliocene experiments will be used within the Pliocene Ice Sheet Model Intercomparison
+Project in order to better constrain the climatological forcing in ice sheet model simulations for
+the Pliocene in the future. There is a well-organized and highly active of community of Pliocene
+climate modellers within PMIP, with the Pliocene working group being one of the most
+successful working groups within PMIP3. The working group is closely associated with the
+United States Geological Survey (USGS) who has had a highly productive core program focused
+on Pliocene environmental reconstruction for the last 25 years, and their data has been used to
+underpin almost all model-data comparisons performed for the Pliocene. Thus, CMIP6 can
+expect a high degree of continued support and new Pliocene data sets from the USGS for
+comparison with model outputs.
+The experiment will address the broad scientific questions:
+  - How does the Earth System respond in the long term to CO2 forcing analogous to that of the modern?
+  - What is the significance of CO2 induced polar amplification for the stability of the ice sheets, sea-ice and sea-level?
+===== Experimental design =====
+Time slice equilibrium climate experiment modifying CO2 (to 400 ppmv), topography, ice sheet
+extent and running with dynamic vegetation (if possible).
+The full description of the experiment can be found on the [[http://geology.er.usgs.gov/egpsc/prism/7.2_pliomip2_data.html|PlioMIP2 web site]].
+The proposed **PMIP-CMIP6 experiment** is described as the **PlioMIP 2 STANDARD experiment** on the PlioMIP 2 site, with boundary conditions summarized in the following table. Please read the pdf document available on the PlioMIP 2 site for a detailed description.
+{{:pmip3:cmip6:design:plio:pliomip_bc_standard.png?400|Click on the table to get a bigger version}}
+Click on the table to get a bigger version