Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth
The last interglacial (LIG, ~130–116 ka, ka = 1000 yr ago) is characterized by high-latitude warming and is therefore often considered as a possible analogue for future warming. However, in contrast to predicted future greenhouse warming, the LIG climate is largely governed by variations in...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-07-01
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| Series: | Climate of the Past |
| Online Access: | http://www.clim-past.net/10/1305/2014/cp-10-1305-2014.pdf |
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| author | P.M. Langebroek K. H. Nisancioglu |
| author_facet | P.M. Langebroek K. H. Nisancioglu |
| author_sort | P.M. Langebroek |
| collection | DOAJ |
| description | The last interglacial (LIG, ~130–116 ka, ka = 1000 yr ago) is characterized by high-latitude
warming and is therefore often considered as a possible analogue for
future warming. However, in contrast to predicted future greenhouse
warming, the LIG climate is largely governed by
variations in insolation. Greenhouse gas (GHG) concentrations were
relatively stable and similar to pre-industrial values, with the
exception of the early LIG when, on average, GHGs were slightly
lower.
<br><br>
We performed six time-slice simulations with the low-resolution
version of the Norwegian Earth System Model covering the LIG.
In four simulations only the orbital forcing was changed.
In two other simulations, representing the early LIG, additionally the GHG forcing was reduced.
<br><br>
With these simulations we investigate (1) the different effects of GHG versus insolation forcing on the temperatures during the LIG;
(2) whether reduced GHGs can explain the low temperatures reconstructed for the North Atlantic; and
(3) the timing of the observed LIG peak warmth.
<br><br>
Our simulations show that the insolation forcing results in seasonal and
hemispheric differences in temperature. In contrast, a reduction in
the GHG forcing causes a global and seasonal-independent
cooling. Furthermore, we compare modelled temperatures with proxy-based
LIG sea-surface temperatures along a transect in the North
Atlantic. The modelled North Atlantic summer sea-surface
temperatures capture the general trend of the reconstructed summer
temperatures, with low values in the early LIG, a peak
around 125 ka, and a steady decrease towards the end of the LIG. Simulations with reduced
GHG forcing improve the model–data fit as they show lower temperatures in the
early LIG. Furthermore we show that the timing of
maximum summer and winter surface temperatures is in line with the local summer and winter insolation
maximum at most latitudes. Two regions where the maximum local insolation and temperature do not occur at the same time
are Antarctica and the Southern Ocean. The austral summer insolation has a late maximum at ~115 ka.
In contrast the austral summer temperatures in Antarctica show
maxima at both ~130 ka and ~115 ka, and the Southern
Ocean temperatures peak only at ~130 ka.
This is probably due to the integrating effect of the
ocean, storing heat from other seasons and resulting in relatively warm austral summer
temperatures.
Reducing the GHG concentrations in the early LIG (125 and 130 ka) results in a similar timing of peak warmth, except over Antarctica.
There, the lower austral summer temperatures at 130 ka shift the maximum warmth to a single peak at 115 ka. |
| first_indexed | 2024-12-23T05:12:20Z |
| format | Article |
| id | doaj.art-20bcc30306894e96af29dbe28438f334 |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-12-23T05:12:20Z |
| publishDate | 2014-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-20bcc30306894e96af29dbe28438f3342022-12-21T17:58:55ZengCopernicus PublicationsClimate of the Past1814-93241814-93322014-07-011041305131810.5194/cp-10-1305-2014Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmthP.M. Langebroek0K. H. Nisancioglu1Bjerknes Centre for Climate Research, Uni Research Climate, Allégaten 55, 5007 Bergen, NorwayBjerknes Centre for Climate Research, Uni Research Climate, Allégaten 55, 5007 Bergen, NorwayThe last interglacial (LIG, ~130–116 ka, ka = 1000 yr ago) is characterized by high-latitude warming and is therefore often considered as a possible analogue for future warming. However, in contrast to predicted future greenhouse warming, the LIG climate is largely governed by variations in insolation. Greenhouse gas (GHG) concentrations were relatively stable and similar to pre-industrial values, with the exception of the early LIG when, on average, GHGs were slightly lower. <br><br> We performed six time-slice simulations with the low-resolution version of the Norwegian Earth System Model covering the LIG. In four simulations only the orbital forcing was changed. In two other simulations, representing the early LIG, additionally the GHG forcing was reduced. <br><br> With these simulations we investigate (1) the different effects of GHG versus insolation forcing on the temperatures during the LIG; (2) whether reduced GHGs can explain the low temperatures reconstructed for the North Atlantic; and (3) the timing of the observed LIG peak warmth. <br><br> Our simulations show that the insolation forcing results in seasonal and hemispheric differences in temperature. In contrast, a reduction in the GHG forcing causes a global and seasonal-independent cooling. Furthermore, we compare modelled temperatures with proxy-based LIG sea-surface temperatures along a transect in the North Atlantic. The modelled North Atlantic summer sea-surface temperatures capture the general trend of the reconstructed summer temperatures, with low values in the early LIG, a peak around 125 ka, and a steady decrease towards the end of the LIG. Simulations with reduced GHG forcing improve the model–data fit as they show lower temperatures in the early LIG. Furthermore we show that the timing of maximum summer and winter surface temperatures is in line with the local summer and winter insolation maximum at most latitudes. Two regions where the maximum local insolation and temperature do not occur at the same time are Antarctica and the Southern Ocean. The austral summer insolation has a late maximum at ~115 ka. In contrast the austral summer temperatures in Antarctica show maxima at both ~130 ka and ~115 ka, and the Southern Ocean temperatures peak only at ~130 ka. This is probably due to the integrating effect of the ocean, storing heat from other seasons and resulting in relatively warm austral summer temperatures. Reducing the GHG concentrations in the early LIG (125 and 130 ka) results in a similar timing of peak warmth, except over Antarctica. There, the lower austral summer temperatures at 130 ka shift the maximum warmth to a single peak at 115 ka.http://www.clim-past.net/10/1305/2014/cp-10-1305-2014.pdf |
| spellingShingle | P.M. Langebroek K. H. Nisancioglu Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth Climate of the Past |
| title | Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth |
| title_full | Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth |
| title_fullStr | Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth |
| title_full_unstemmed | Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth |
| title_short | Simulating last interglacial climate with NorESM: role of insolation and greenhouse gases in the timing of peak warmth |
| title_sort | simulating last interglacial climate with noresm role of insolation and greenhouse gases in the timing of peak warmth |
| url | http://www.clim-past.net/10/1305/2014/cp-10-1305-2014.pdf |
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