Twenty-First-Century Multimodel Subtropical Precipitation Declines Are Mostly Midlatitude Shifts

2012 ◽  
Vol 25 (12) ◽  
pp. 4330-4347 ◽  
Author(s):  
Jack Scheff ◽  
Dargan Frierson
Keyword(s):  
General Circulation ◽  
Storm Track ◽  
First Century ◽  
Intergovernmental Panel ◽  
Common Framework ◽  
Tropical Areas ◽  
Twenty First Century ◽  
Thermodynamic Mechanism ◽  
Precipitation Changes ◽  
Poleward Expansion

Abstract Declines in subtropical precipitation are a robust response to modeled twenty-first-century global warming. Two suggested mechanisms are the “dry-get-drier” intensification of existing subtropical dry zones due to the thermodynamic increase in vapor transport and the poleward expansion of these same dry zones due to poleward shifts in the modeled general circulation. Here, subtropical drying in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report multimodel archive is compared to each of these two mechanisms. Each model’s particular, biased, and seasonally and zonally varying mean state is considered relative to the location of that model’s predicted changes, and these relationships are recorded in a common framework that can be compared across models. The models have a strong tendency to reduce precipitation along the subtropical flanks of their existing midlatitude cyclonic precipitation belts. This broad result agrees with the poleward expansion mechanism and with a poleward storm-track shift in particular. In contrast, the models have no clear tendency to reduce precipitation in the central nor equatorward portions of their subtropical dry zones, implying that the thermodynamic mechanism is broadly unimportant for the precipitation reductions. This is unlike the response of precipitation minus evaporation, which robustly declines in large portions of these regions, especially over the oceans. The models also tend to increase precipitation in their wet deep tropical areas, but this is not as robust as the above reduction in the subtropical midlatitudes. High-latitude precipitation increases are the most robust precipitation changes of all in this framework.

scholarly journals When could global warming reach 4°C?

2011 ◽  
Vol 369 (1934) ◽  
pp. 67-84 ◽  
Author(s):  
Richard A. Betts ◽  
Matthew Collins ◽  
Deborah L. Hemming ◽  
Chris D. Jones ◽  
Jason A. Lowe ◽  
...  
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Carbon Cycle ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
First Century ◽  
Intergovernmental Panel ◽  
Twenty First Century ◽  
Emissions Scenario

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) assessed a range of scenarios of future greenhouse-gas emissions without policies to specifically reduce emissions, and concluded that these would lead to an increase in global mean temperatures of between 1.6°C and 6.9°C by the end of the twenty-first century, relative to pre-industrial. While much political attention is focused on the potential for global warming of 2°C relative to pre-industrial, the AR4 projections clearly suggest that much greater levels of warming are possible by the end of the twenty-first century in the absence of mitigation. The centre of the range of AR4-projected global warming was approximately 4°C. The higher end of the projected warming was associated with the higher emissions scenarios and models, which included stronger carbon-cycle feedbacks. The highest emissions scenario considered in the AR4 (scenario A1FI) was not examined with complex general circulation models (GCMs) in the AR4, and similarly the uncertainties in climate–carbon-cycle feedbacks were not included in the main set of GCMs. Consequently, the projections of warming for A1FI and/or with different strengths of carbon-cycle feedbacks are often not included in a wider discussion of the AR4 conclusions. While it is still too early to say whether any particular scenario is being tracked by current emissions, A1FI is considered to be as plausible as other non-mitigation scenarios and cannot be ruled out. (A1FI is a part of the A1 family of scenarios, with ‘FI’ standing for ‘fossil intensive’. This is sometimes erroneously written as A1F1, with number 1 instead of letter I.) This paper presents simulations of climate change with an ensemble of GCMs driven by the A1FI scenario, and also assesses the implications of carbon-cycle feedbacks for the climate-change projections. Using these GCM projections along with simple climate-model projections, including uncertainties in carbon-cycle feedbacks, and also comparing against other model projections from the IPCC, our best estimate is that the A1FI emissions scenario would lead to a warming of 4°C relative to pre-industrial during the 2070s. If carbon-cycle feedbacks are stronger, which appears less likely but still credible, then 4°C warming could be reached by the early 2060s in projections that are consistent with the IPCC’s ‘likely range’.

scholarly journals Impact of Climate Drift on Twenty-First-Century Projection in a Coupled Atmospheric–Ocean General Circulation Model

2013 ◽  
Vol 70 (10) ◽  
pp. 3321-3327 ◽  
Author(s):  
Mao-Chang Liang ◽  
Li-Ching Lin ◽  
Ka-Kit Tung ◽  
Yuk L. Yung ◽  
Shan Sun
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
General Circulation Models ◽  
Forced Response ◽  
First Century ◽  
Intergovernmental Panel ◽  
Climate Drift ◽  
Ocean General Circulation ◽  
Twenty First Century ◽  
The Impact

Abstract Reducing climate drift in coupled atmosphere–ocean general circulation models (AOGCMs) usually requires 1000–2000 years of spinup, which has not been practical for every modeling group to do. For the purpose of evaluating the impact of climate drift, the authors have performed a multimillennium-long control run of the Goddard Institute for Space Studies model (GISS-EH) AOGCM and produced different twentieth-century historical simulations and subsequent twenty-first-century projections by branching off the control run at various stages of equilibration. The control run for this model is considered at quasi equilibration after a 1200-yr spinup from a cold start. The simulations that branched off different points after 1200 years are robust, in the sense that their ensemble means all produce the same future projection of warming, both in the global mean and in spatial detail. These robust projections differ from the one that was originally submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), which branched off a not-yet-equilibrated control run. The authors test various common postprocessing schemes in removing climate drift caused by a not-yet-equilibrated ocean initial state and find them to be ineffective, judging by the fact that they differ from each other and from the robust results that branched off an equilibrated control. The authors' results suggest that robust twenty-first-century projections of the forced response can be achieved by running climate simulations from an equilibrated ocean state, because memory of the different initial ocean state is lost in about 40 years if the forced run is started from a quasi-equilibrated state.

Are Changes in Global Precipitation Constrained by the Tropospheric Energy Budget?

2009 ◽  
Vol 22 (3) ◽  
pp. 499-517 ◽  
Author(s):  
F. Hugo Lambert ◽  
Myles R. Allen
Keyword(s):  
Greenhouse Gas ◽  
Black Carbon ◽  
Energy Budget ◽  
General Circulation ◽  
Circulation Model ◽  
First Century ◽  
Aerosol Forcing ◽  
Twenty First Century ◽  
Precipitation Changes ◽  
Global Precipitation

Abstract A tropospheric energy budget argument is used to analyze twentieth-century precipitation changes. It is found that global and ocean-mean general circulation model (GCM) precipitation changes can be understood as being due to the competing direct and surface-temperature-dependent effects of external climate forcings. In agreement with previous work, precipitation is found to respond more strongly to anthropogenic and volcanic sulfate aerosol and solar forcing than to greenhouse gas and black carbon aerosol forcing per unit temperature. This is due to the significant direct effects of greenhouse gas and black carbon forcing. Given that the relative importance of different forcings may change in the twenty-first century, the ratio of global precipitation change to global temperature change may be quite different. Differences in GCM twentieth- and twenty-first-century values are tractable via the energy budget framework in some, but not all, models. Changes in land-mean precipitation, on the other hand, cannot be understood at all with the method used here, even if land–ocean heat transfer is considered. In conclusion, the tropospheric energy budget is a useful concept for understanding the precipitation response to different forcings but it does not fully explain precipitation changes even in the global mean.

scholarly journals Probabilistic Projections of Climate Change over China under the SRES A1B Scenario Using 28 AOGCMs

2011 ◽  
Vol 24 (17) ◽  
pp. 4741-4756 ◽  
Author(s):  
Weilin Chen ◽  
Zhihong Jiang ◽  
Laurent Li
Keyword(s):  
Climate Change ◽  
Interannual Variability ◽  
General Circulation ◽  
Regional Scale ◽  
First Century ◽  
Climate System Model ◽  
Huai River ◽  
Twenty First Century ◽  
The Impact ◽  
A1b Scenario

Probabilistic projection of climate change consists of formulating the climate change information in a probabilistic manner at either global or regional scale. This can produce useful results for studies of the impact of climate change impact and change mitigation. In the present study, a simple yet effective approach is proposed with the purpose of producing probabilistic results of climate change over China for the middle and end of the twenty-first century under the Special Report on Emissions Scenarios A1B (SRES A1B) emission scenario. Data from 28 coupled atmosphere–ocean general circulation models (AOGCMs) are used. The methodology consists of ranking the 28 models, based on their ability to simulate climate over China in terms of two model evaluation metrics. Different weights were then given to the models according to their performances in present-day climate. Results of the evaluation for the current climate show that five models that have relatively higher resolutions—namely, the Istituto Nazionale di Geofisica e Vulcanologia ECHAM4 (INGV ECHAM4), the third climate configuration of the Met Office Unified Model (UKMO HadCM3), the CSIRO Mark version 3.5 (Mk3.5), the NCAR Community Climate System Model, version 3 (CCSM3), and the Model for Interdisciplinary Research on Climate 3.2, high-resolution version [MIROC3.2 (hires)]—perform better than others over China. Their corresponding weights (normalized to 1) are 0.289, 0.096, 0.058, 0.048, and 0.044, respectively. Under the A1B scenario, surface air temperature is projected to increase significantly for both the middle and end of the twenty-first century, with larger magnitude over the north and in winter. There are also significant increases in rainfall in the twenty-first century under the A1B scenario, especially for the period 2070–99. As far as the interannual variability is concerned, the most striking feature is that there are high probabilities for the future intensification of interannual variability of precipitation over most of China in both winter and summer. For instance, over the Yangtze–Huai River basin (28°–35°N, 105°–120°E), there is a 60% probability of increased interannual standard deviation of precipitation by 20% in summer, which is much higher than that of the mean precipitation. In general there are small differences between weighted and unweighted projections, but the uncertainties in the projected changes are reduced to some extent after weighting.

scholarly journals Trends in Storm-Triggered Landslides over Southern California

2014 ◽  
Vol 53 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Diandong Ren ◽  
Lance M. Leslie ◽  
Mervyn J. Lynch
Keyword(s):  
Extreme Precipitation ◽  
Southern California ◽  
Extreme Rainfall ◽  
First Century ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Intergovernmental Panel ◽  
Extreme Precipitation Events ◽  
Landslide Frequency ◽  
Twenty First Century ◽  
Precipitation Events

AbstractChanges in storm-triggered landslide activity for Southern California in a future warming climate are estimated using an advanced, fully three-dimensional, process-based landslide model, the Scalable and Extensible Geofluid Modeling System for landslides (SEGMENT-Landslide). SEGMENT-Landslide is driven by extreme rainfall projections from the Geophysical Fluid Dynamics Laboratory High Resolution Atmospheric Model (GFDL-HIRAM). Landslide changes are derived from GFDL-HIRAM forcing for two periods: 1) the twentieth century (CNTRL) and 2) the twenty-first century under the moderate Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A1B enhanced greenhouse gas emissions scenario (EGHG). Here, differences are calculated in landslide frequency and magnitude between the CNTRL and EGHG projections; kernel density estimation (KDE) is used to determine differences in projected landslide locations. This study also reveals that extreme precipitation events in Southern California are strongly correlated with several climate drivers and that GFDL-HIRAM simulates well the southern (relative to Aleutian synoptic systems) storm tracks in El Niño years and the rare (~27-yr recurrence period) hurricane-landfalling events. GFDL-HIRAM therefore can provide satisfactory projections of the geographical distribution, seasonal cycle, and interannual variability of future extreme precipitation events (>50 mm) that have possible landslide consequences for Southern California. Although relatively infrequent, extreme precipitation events contribute most of the annual total precipitation in Southern California. Two findings of this study have major implications for Southern California. First is a possible increase in landslide frequency and areal distribution during the twenty-first century. Second, the KDE reveals three clusters in both the CNTRL and EGHG model mean scarp positions, with a future eastward (inland) shift of ~0.5° and a northward shift of ~1°. These findings suggest that previously stable areas might become susceptible to storm-triggered landslides in the twenty-first century.

scholarly journals Quantifying Sources of Uncertainty in Projections of Future Climate*

2014 ◽  
Vol 27 (23) ◽  
pp. 8793-8808 ◽  
Author(s):  
Paul J. Northrop ◽  
Richard E. Chandler
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Internal Variability ◽  
Future Climate ◽  
First Century ◽  
Climate Projections ◽  
Large Contribution ◽  
Sources Of Uncertainty ◽  
Twenty First Century ◽  
Emissions Scenario

Abstract A simple statistical model is used to partition uncertainty from different sources, in projections of future climate from multimodel ensembles. Three major sources of uncertainty are considered: the choice of climate model, the choice of emissions scenario, and the internal variability of the modeled climate system. The relative contributions of these sources are quantified for mid- and late-twenty-first-century climate projections, using data from 23 coupled atmosphere–ocean general circulation models obtained from phase 3 of the Coupled Model Intercomparison Project (CMIP3). Similar investigations have been carried out recently by other authors but within a statistical framework for which the unbalanced nature of the data and the small number (three) of scenarios involved are potentially problematic. Here, a Bayesian analysis is used to overcome these difficulties. Global and regional analyses of surface air temperature and precipitation are performed. It is found that the relative contributions to uncertainty depend on the climate variable considered, as well as the region and time horizon. As expected, the uncertainty due to the choice of emissions scenario becomes more important toward the end of the twenty-first century. However, for midcentury temperature, model internal variability makes a large contribution in high-latitude regions. For midcentury precipitation, model internal variability is even more important and this persists in some regions into the late century. Implications for the design of climate model experiments are discussed.

Past, present and future precipitation in the Middle East: insights from models and observations

2010 ◽  
Vol 368 (1931) ◽  
pp. 5173-5184 ◽  
Author(s):  
Emily Black ◽  
David J. Brayshaw ◽  
Claire M. C. Rambeau
Keyword(s):  
Middle East ◽  
Climate Models ◽  
Climate Model ◽  
Storm Track ◽  
First Century ◽  
Southern Europe ◽  
The Holocene ◽  
The North ◽  
The Mediterranean ◽  
Twenty First Century

Anthropogenic changes in precipitation pose a serious threat to society—particularly in regions such as the Middle East that already face serious water shortages. However, climate model projections of regional precipitation remain highly uncertain. Moreover, standard resolution climate models have particular difficulty representing precipitation in the Middle East, which is modulated by complex topography, inland water bodies and proximity to the Mediterranean Sea. Here we compare precipitation changes over the twenty-first century against both millennial variability during the Holocene and interannual variability in the present day. In order to assess the climate model and to make consistent comparisons, this study uses new regional climate model simulations of the past, present and future in conjunction with proxy and historical observations. We show that the pattern of precipitation change within Europe and the Middle East projected by the end of the twenty-first century has some similarities to that which occurred during the Holocene. In both cases, a poleward shift of the North Atlantic storm track and a weakening of the Mediterranean storm track appear to cause decreased winter rainfall in southern Europe and the Middle East and increased rainfall further north. In contrast, on an interannual time scale, anomalously dry seasons in the Middle East are associated with a strengthening and focusing of the storm track in the north Mediterranean and hence wet conditions throughout southern Europe.

Impact of Climate Change on River Discharge Projected by Multimodel Ensemble

2006 ◽  
Vol 7 (5) ◽  
pp. 1076-1089 ◽  
Author(s):  
Daisuke Nohara ◽  
Akio Kitoh ◽  
Masahiro Hosaka ◽  
Taikan Oki
Keyword(s):  
River Discharge ◽  
Mediterranean Region ◽  
General Circulation ◽  
River Flow ◽  
Central Africa ◽  
General Circulation Models ◽  
First Century ◽  
Upstream Region ◽  
The Mediterranean ◽  
Twenty First Century

Abstract This study investigates the projections of river discharge for 24 major rivers in the world during the twenty-first century simulated by 19 coupled atmosphere–ocean general circulation models based on the Special Report on Emissions Scenarios A1B scenario. To reduce model bias and uncertainty, a weighted ensemble mean (WEM) is used for multimodel projections. Although it is difficult to reproduce the present river discharge in any single model, the WEM results produce more accurate reproduction for most rivers, except those affected by anthropogenic water usage. At the end of the twenty-first century, the annual mean precipitation, evaporation, and runoff increase in high latitudes of the Northern Hemisphere, southern to eastern Asia, and central Africa. In contrast, they decrease in the Mediterranean region, southern Africa, southern North America, and Central America. Although the geographical distribution of the changes in precipitation and runoff tends to coincide with that in the river discharge, it should be emphasized that the change in runoff at the upstream region affects the river flow in the downstream region. In high-latitude rivers (Amur, Lena, MacKenzie, Ob, Yenisei, and Yukon), the discharge increases, and the peak timing shifts earlier because of an earlier snowmelt caused by global warming. Discharge tends to decrease for the rivers in Europe to the Mediterranean region (Danube, Euphrates, and Rhine), and southern United Sates (Rio Grande).

Twenty-First-Century Snowfall and Snowpack Changes over the Southern California Mountains

2015 ◽  
Vol 29 (1) ◽  
pp. 91-110 ◽  
Author(s):  
Fengpeng Sun ◽  
Alex Hall ◽  
Marla Schwartz ◽  
Daniel B. Walton ◽  
Neil Berg
Keyword(s):  
General Circulation ◽  
Southern California ◽  
Snow Water Equivalent ◽  
Coupled Model ◽  
General Circulation Models ◽  
First Century ◽  
Climate Projections ◽  
Rcp Scenarios ◽  
Ensemble Mean ◽  
Twenty First Century

Abstract Future snowfall and snowpack changes over the mountains of Southern California are projected using a new hybrid dynamical–statistical framework. Output from all general circulation models (GCMs) in phase 5 of the Coupled Model Intercomparison Project archive is downscaled to 2-km resolution over the region. Variables pertaining to snow are analyzed for the middle (2041–60) and end (2081–2100) of the twenty-first century under two representative concentration pathway (RCP) scenarios: RCP8.5 (business as usual) and RCP2.6 (mitigation). These four sets of projections are compared with a baseline reconstruction of climate from 1981 to 2000. For both future time slices and scenarios, ensemble-mean total winter snowfall loss is widespread. By the mid-twenty-first century under RCP8.5, ensemble-mean winter snowfall is about 70% of baseline, whereas the corresponding value for RCP2.6 is somewhat higher (about 80% of baseline). By the end of the century, however, the two scenarios diverge significantly. Under RCP8.5, snowfall sees a dramatic further decline; 2081–2100 totals are only about half of baseline totals. Under RCP2.6, only a negligible further reduction from midcentury snowfall totals is seen. Because of the spread in the GCM climate projections, these figures are all associated with large intermodel uncertainty. Snowpack on the ground, as represented by 1 April snow water equivalent is also assessed. Because of enhanced snowmelt, the loss seen in snowpack is generally 50% greater than that seen in winter snowfall. By midcentury under RCP8.5, warming-accelerated spring snowmelt leads to snow-free dates that are about 1–3 weeks earlier than in the baseline period.

Attribution of Projected Changes in Atmospheric Moisture Transport in the Arctic: A Self-Organizing Map Perspective

2009 ◽  
Vol 22 (15) ◽  
pp. 4135-4153 ◽  
Author(s):  
Natasa Skific ◽  
Jennifer A. Francis ◽  
John J. Cassano
Keyword(s):  
Twentieth Century ◽  
Moisture Transport ◽  
First Century ◽  
The Arctic ◽  
Self Organizing Map ◽  
Total Change ◽  
Intergovernmental Panel ◽  
Climate System Model ◽  
Twenty First Century ◽  
Self Organizing

Abstract Meridonal moisture transport into the Arctic derived from one simulation of the National Center for Atmospheric Research Community Climate System Model (CCSM3), spanning the periods of 1960–99, 2010–30, and 2070–89, is analyzed. The twenty-first-century simulation incorporates the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 scenario for CO2 and sulfate emissions. Modeled and observed [from the 40-yr ECMWF Re-Analysis (ERA-40)] sea level pressure (SLP) fields are classified using a neural network technique called self-organizing maps to distill a set of characteristic atmospheric circulation patterns over the region north of 60°N. Model performance is validated for the twentieth century by comparing the frequencies of occurrence of particular circulation regimes in the model to those from the ERA-40. The model successfully captures dominant SLP patterns, but differs from observations in the frequency with which certain patterns occur. The model’s twentieth-century vertical mean moisture transport profile across 70°N compares well in terms of structure but exceeds the observations by about 12% overall. By relating moisture transport to a particular circulation regime, future changes in moisture transport across 70°N are assessed and attributed to changes in frequency with which the atmosphere resides in particular SLP patterns and/or to other factors, such as changes in the meridional moisture gradient. By the late twenty-first century, the transport is projected to increase by about 21% in this model realization, with the largest contribution (32%) to the total change occurring in summer. Only about one-quarter of the annual increase is due to changes in pattern occupancy, suggesting that the majority is related to mainly thermodynamic factors. A larger poleward moisture transport likely constitutes a positive feedback on the system through related increases in latent heat release and the emission of longwave radiation to the surface.

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