Energy Balance Climate Model Research Articles

Periodicity in an energy balance climate model

Periodicity in an energy balance climate model

Habitable Planets with High Obliquities

Earth's obliquity would vary chaotically from 0° to 85° were it not for the presence of the Moon (J. Laskar, F. Joutel, and P. Robutel, 1993,Nature361,615–617). The Moon itself is thought to be an accident of accretion, formed by a glancing blow from a Mars-sized planetesimal. Hence, planets with similar moons and stable obliquities may be extremely rare. This has lead Laskar and colleagues to suggest that the number of Earth-like planets with high obliquities and temperate, life-supporting climates may be small.To test this proposition, we have used an energy-balance climate model to simulate Earth's climate at obliquities up to 90°. We show that Earth's climate would become regionally severe in such circumstances, with large seasonal cycles and accompanying temperature extremes on middle- and high-latitude continents which might be damaging to many forms of life. The response of other, hypothetical, Earth-like planets to large obliquity fluctuations depends on their land–sea distribution and on their position within the habitable zone (HZ) around their star. Planets with several modest-sized continents or equatorial supercontinents are more climatically stable than those with polar supercontinents. Planets farther out in the HZ are less affected by high obliquities because their atmospheres should accumulate CO2in response to the carbonate–silicate cycle. Dense, CO2-rich atmospheres transport heat very effectively and therefore limit the magnitude of both seasonal cycles and latitudinal temperature gradients. We conclude that a significant fraction of extrasolar Earth-like planets may still be habitable, even if they are subject to large obliquity fluctuations.

Projections of global mean sea level rise calculated with a 2D energy-balance climate model and dynamic ice sheet models

Projections of global mean sea level rise calculated with a 2D energy-balance climate model and dynamic ice sheet models

An integrated modeling approach to global carbon and nitrogen cycles: Balancing their budgets

A modeling attempt is presented to describe the global carbon and nitrogen cycle: where it originates, where it stays, and how the global carbon and nitrogen budgets can be balanced. We used integrated but simple box models: a coupled global carbon‐nitrogen cycle and climate model. The global carbon‐nitrogen cycle model describes on a global scale the exchange fluxes between the compartments and their main internal processes and different biogeochemical feedbacks (e.g., for CO2 and N fertilization and for temperature). The coupled model also includes an energy balance climate model, using as input the induced radiative forcing of greenhouse gases and sulfate aerosols. Simulation experiments performed with the coupled model showed that by incorporating only the CO2 fertilization and temperature‐related feedbacks a balanced past carbon budget could not be created. Therefore the N fertilization of the anthropogenic nitrogen depositions for temperate forests, which depends on the fate of the anthropogenic nitrogen inputs, must be included. By varying the N fluxes by river transport, and deposition and denitrification, a balanced past nitrogen budget was obtained. This resulted in an anthropogenic deposition of 40 Tg N yr−1 for the temperate forests and a N fertilization which constitutes 20–50% of the missing carbon sink. Finally, the future fate of anthropogenic emissions of the C and mobilization of the N compounds were projected given the condition of balanced carbon and nitrogen budgets.

Dansgaard–Oeschger Oscillations in a Coupled Atmosphere–Ocean Climate Model

Abstract A reduced model of the global thermohaline circulation has been asynchronously coupled to a simple energy balance climate model in order to investigate the natural variability of the overturning circulation that may have been characteristic of late glacial conditions. Previous analyses with the ocean-only component of the model have suggested that the nature of the internal variability of the thermohaline circulation was a strong function of the surface boundary conditions on temperature and salinity flux. When the boundary conditions were altered from those corresponding to modern conditions to those appropriate to full glacial conditions, then the internal variability was shown to be radically transformed. Under modern conditions the ocean-only version of the model delivered an overturning circulation that was only weakly time dependent with a characteristic period of centuries. Under full glacial boundary conditions, however, the circulation became strongly time dependent with a characteristic...

A high-resolution model of the 100 ka ice-age cycle

Significant improvements to the representation of climate forcing and mass-balance response in a coupled two-dimensional global energy balance climate model (EBM) and vertically integrated ice-sheet model (ISM) have led to the prediction of an ice-volume chronology for the most recent ice-age cycle of the Northern Hemisphere that is close to that inferred from the geological record. Most significant is that full glacial termination is delivered by the model without the need for new physical ingredients. In addition, a relatively close match is achieved between the Last Glacial Maximum (LGM) model ice topography and that of the recently-described ICE-4G reconstruction. These results suggest that large-scale climate system reorganization is not required to explain the main variations of the North American (NA) ice sheets over the last glacial cycle. Lack of sea-ice and marine-ice dynamics in the model leaves the situation over the Eurasian (EA) sector much more uncertain.The incorporation of a gravitationally self-consistent description of the glacial isostatic adjustment process demonstrates that the NA and EA bedrock responses can be adequately represented by simpler damped-relaxation models with characteristic time-scales of 3–5ka and 5 ka, respectively. These relaxation times agree with those independently inferred on the basis of postglacial relative sea-level histories.

Asynchronously coupling the cryosphere and atmosphere in an energy-balance climate model

A major component of the climate system on the 10 000-100 000 year time-scales is continental ice sheets, yet many of the mechanisms involved in the land-sea-ice processes that affect the ice sheets are poorly understood. In order to examine these processes in more detail, we have developed a coupled energy balance climate-thermodynamic sea-ice—continental-ice-sheet model (CCSLI model). This model includes a hydrologic cycle, a detailed surface energy and mass balance, a thermodynamic sea-ice model, and a zonally averaged dynamic ice-flow model with bedrock depression.Because of the variety of space and time-scales inherent in such a model, we have asynchronously coupled the land—ice model to the other components of the model. In this paper the asynchronous coupling is described and sensitivity studies are presented that determine the values of the asynchronous coupling parameters. Model simulations using these values allow the model to run nearly ten times faster with minimal changes in the final state of the ice sheet.

Asynchronously coupling the cryosphere and atmosphere in an energy-balance climate model

A major component of the climate system on the 10 000-100 000 year time-scales is continental ice sheets, yet many of the mechanisms involved in the land-sea-ice processes that affect the ice sheets are poorly understood. In order to examine these processes in more detail, we have developed a coupled energy balance climate-thermodynamic sea-ice—continental-ice-sheet model (CCSLI model). This model includes a hydrologic cycle, a detailed surface energy and mass balance, a thermodynamic sea-ice model, and a zonally averaged dynamic ice-flow model with bedrock depression.Because of the variety of space and time-scales inherent in such a model, we have asynchronously coupled the land—ice model to the other components of the model. In this paper the asynchronous coupling is described and sensitivity studies are presented that determine the values of the asynchronous coupling parameters. Model simulations using these values allow the model to run nearly ten times faster with minimal changes in the final state of the ice sheet.

Projections of global mean sea level rise calculated with a 2D energy-balance climate model and dynamic ice sheet models

Projections of changes in surface air temperature and global mean sea level over the next century are presented for all IS92 radiative forcing scenarios. A zonal mean energy-balance climate model is used to estimate temperature changes and thermal expansion, precipitation-dependent sensitivity values are used to estimate the sea-level contribution of glaciers and small ice caps and dynamic ice-sheet models coupled to surface mass balance models are employed with regard to the Greenland and Antarctic ice sheets. A few of the sea-level projections have been included in the IPCC96-report for comparison with the revised IPCC96 projections. Here it is demonstrated that the observed inter-model differences are similar for all IS92 radiative forcing scenarios: the projections of global surface air temperature change resemble the revised IPCC96 projections, but the projections of global sea-level rise are 30%—50% smaller than the revised IPCC96 projections. In this paper, the reasons for the inter-model differences in sea-level results are considered. The largest inter-model differences in individual sea-level contributions are found for thermal expansion and for the Antarctic ice-sheet. Sensitivity experiments are presented that show the importance of different assumptions about the temperature forcing of the glacier and ice-sheet models and about weakening of the ocean circulation. Furthermore, uncertainties in thermal expansion caused by uncertainties in ocean heat mixing are considered. It is concluded that the inter-model differences in sea-level projections are caused by the use of essentially different models in this paper and in the revised IPCC96 projections.

A high-resolution model of the 100 ka ice-age cycle

Significant improvements to the representation of climate forcing and mass-balance response in a coupled two-dimensional global energy balance climate model (EBM) and vertically integrated ice-sheet model (ISM) have led to the prediction of an ice-volume chronology for the most recent ice-age cycle of the Northern Hemisphere that is close to that inferred from the geological record. Most significant is that full glacial termination is delivered by the model without the need for new physical ingredients. In addition, a relatively close match is achieved between the Last Glacial Maximum (LGM) model ice topography and that of the recently-described ICE-4G reconstruction. These results suggest that large-scale climate system reorganization is not required to explain the main variations of the North American (NA) ice sheets over the last glacial cycle. Lack of sea-ice and marine-ice dynamics in the model leaves the situation over the Eurasian (EA) sector much more uncertain.The incorporation of a gravitationally self-consistent description of the glacial isostatic adjustment process demonstrates that the NA and EA bedrock responses can be adequately represented by simpler damped-relaxation models with characteristic time-scales of 3–5ka and 5 ka, respectively. These relaxation times agree with those independently inferred on the basis of postglacial relative sea-level histories.

Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

AbstractMost dynamic ice-sheet studies currently use either empirically based parameterizations or simple energy-balance climate models for the surface mass-balance forcing. If three-dimensional global climate models (GCMs) could be used instead, they would greatly improve the potential realism of coupled climate ice-sheet simulations. However, there are two serious problems in simulating realistic mass balances on ice sheets from GCM simulations: (i) dynamic ice-sheet models and the underlying bedrock topography need horizontal resolution of 50–100 km or less, but the finest practical resolution of atmospheric GCMs is currently ˜250 km, and (ii) GCM surface physics usually neglects the local refreezing of meltwater on ice sheets.Two techniques are described that address these problems: an elevation correction applied to the atmospheric GCM fields interpolated to the ice-sheet grid, and a refreezing correction involving the annual totals of snowfall, rainfall and local melt at each grid-point. As an example of their use, we have used the GENESIS version 2 GCM at 3.75° × 3.75° resolution to simulate the climate at the end of the last interglaciation at ˜116 000 years ago. The atmospheric climate is then used to drive a standard two-dimensional dynamic ice-sheet model for 10 000 years on a 0.5° × 0.5° grid spanning northern North America. The model successfully predicts ice-sheet initiation over the Baffin Island highlands and the Canadian Archipelago, but at a slower rate than observed. A large ice sheet nucleates and grows rapidly over the northwestern Rockies, in conflict with geologic evidence. Possible reasons for these discrepancies are discussed.

Detection of the Climate Response to the Solar Cycle

Abstract Optimal space–time signal processing is used to infer the amplitude of the large-scale, near-surface temperature response to the, “11 year” solar cycle. The estimation procedure involves the following stops. 1) By correlating 14 years of monthly total solar irradiance measurements made by the Nimbus-7 satellite and monthly Wolf sunspot numbers, a monthly solar irradiance forcing function is constructed for the years 1894–1993. 2) Using this forcing function, a space-time waveform of the climate response for the same 100 years is generated from an energy balance climate model. 3) The space-time covariance statistics in the frequency band (16.67 yr)−1–(7.14 yr)−1 are calculated using control runs from two different coupled ocean-atmosphere global climate models. 4) Using the results from the last two stops, an optimal filter is constructed and applied to observed surface temperature data for the years 1894–1993. 5) An estimate of the ratio of the real climate response, contained in the observed dat...

On a two-dimensional energy balance climate model coupled interactively to a land carbon cycle model

On a two-dimensional energy balance climate model coupled interactively to a land carbon cycle model

The effect of reduced ocean overturning on the climate of the last glacial maximum

This study focuses on the differences between the present-day climate and the climate of the last glacial maximum (LGM) of 18 000 y BP using a zonally averaged energy balance climate model. The ocean is represented by a 2-D model with prescribed overturning pattern in which the overturning velocities can be adjusted freely. We discuss what influence the use of ice-age conditions (i.e. enhanced land-ice cover, reduced CO2-concentration and reduced oceanic overturning rate) has on the differences between ice-age and present-day climate. When compared to LGM sea-surface temperatures derived from proxy data, the model is able to simulate fairly well the important features of the meridional distribution of these temperature differences. Applying reduced ocean overturning rates during the LGM significantly decreases poleward heat transport in the oceans, thereby allowing for additional cooling of the polar regions and less cooling of the equatorial region. As a result, the agreement with CLIMAP proxy temperature differences increases, especially in the equatorial region. This mechanism can explain the slight differences in the CLIMAP proxy equatorial surface temperatures between the LGM and the present-day climate.

The effect of reduced ocean overturning on the climate of the last glacial maximum

This study focuses on the differences between the present-day climate and the climate of the last glacial maximum (LGM) of 18 000 y BP using a zonally averaged energy balance climate model. The ocean is represented by a 2-D model with prescribed overturning pattern in which the overturning velocities can be adjusted freely. We discuss what influence the use of ice-age conditions (i.e. enhanced land-ice cover, reduced CO2-concentration and reduced oceanic overturning rate) has on the differences between ice-age and present-day climate. When compared to LGM sea-surface temperatures derived from proxy data, the model is able to simulate fairly well the important features of the meridional distribution of these temperature differences. Applying reduced ocean overturning rates during the LGM significantly decreases poleward heat transport in the oceans, thereby allowing for additional cooling of the polar regions and less cooling of the equatorial region. As a result, the agreement with CLIMAP proxy temperature differences increases, especially in the equatorial region. This mechanism can explain the slight differences in the CLIMAP proxy equatorial surface temperatures between the LGM and the present-day climate.

AN OPTIMAL METHOD TO ESTIMATE THE SPHERICAL HARMONIC COMPONENTS OF THE SURFACE AIR TEMPERATURE

This paper describes a method that minimizes the mean squared error (MSE) in estimating the spherical harmonic components of the surface air temperature field. The ratio of the MSE to the variance of the spherical harmonic component is expressed in terms of the length scale λ0, and the positions and weights of the measurement stations. The weights are optimized by the condition of minimizing the sampling error. To present an analytical example, we assume the homogeneous statistics of the temperature anomaly field, and take the low frequency approximation (i.e. ignoring the time dependence). The spectra of the temperature anomaly are the coefficients of a Fourier–Legendre series of the covariance function, and they are analytically derived from a linear noise forced energy balance climate model. Consequently, the MSE, the percentage sampling error, and the signal–noise ratio are computed for a given network of stations. Our results show that: (i) the sampling errors computed from both optimal weights and uniform weights increase with respect to the order of the spherical harmonic component; (ii) the sampling errors computed from optimal weights are significantly smaller than those from uniform weights for sufficiently dense networks. With about 60 reasonably positioned stations for sampling the spherical harmonic components 00 T10 and T11, one can get the sampling error below 10 per cent when the optimal weights are applied. An experiment with 210 stations produces the sampling errors of less than 10 per cent for the spherical harmonic components from T00 up to T54

A seasonal energy-balance climate model for coupling to ice-sheet models

An energy-balance climate model designed for coupling to ice-sheet models is presented. Its independent variables are longitude, latitude and time of the year. The model is based on the vertically integrated equations of conservation of energy and humidity. It can predict the vertically averaged temperature. Since it includes a hydrological cycle, it can also diagnose the net fresh-water flux and hence the annual snow budget at the atmosphere–ice-sheet interface. To this end, the model does not require observed precipitation rates. The computational cost is reduced by using an analytically computed Fourier–Legendre representation of daily insolation. For a highly idealized test-case configuration, two simple sensitivity experiments are carried out.

A seasonal energy-balance climate model for coupling to ice-sheet models

An energy-balance climate model designed for coupling to ice-sheet models is presented. Its independent variables are longitude, latitude and time of the year. The model is based on the vertically integrated equations of conservation of energy and humidity. It can predict the vertically averaged temperature. Since it includes a hydrological cycle, it can also diagnose the net fresh-water flux and hence the annual snow budget at the atmosphere–ice-sheet interface. To this end, the model does not require observed precipitation rates. The computational cost is reduced by using an analytically computed Fourier–Legendre representation of daily insolation. For a highly idealized test-case configuration, two simple sensitivity experiments are carried out.

On a two-dimensional energy balance climate model coupled interactively to a land carbon cycle model

A two-dimensional (latitude-height) climate/global carbon cycle model has been developed to investigate the interactive climate/biogeochemical response of a land biosphere to a linearly increasing input of carbon totalling 1000 Gtons C into the atmosphere over a 150-years period. With no fertilization response to the increasing CO 2 content in the atmosphere (fertilization factor = 0.0), the land biosphere acts as a net source of CO 2 for the atmosphere. This is mainly due to the soil carbon response to increasing surface temperatures, resulting in a greater soil release than the uptake of carbon by NPP. At the end of 150 years, globally averaged NPP has increased by about 2.3 Gtons C yr −1 , while the soil respiration has increased by 3.9 Gtons C yr −1 . When the land biosphere is allowed to respond to the increasing atmospheric CO 2 (fertilization factor = 0.3), NPP increases at a much faster rate than the soil release, causing the land biosphere to become a net sink for the excess CO 2 in the atmosphere. In this case, NPP has increased by about 15.4 Gtons C yr −1 , while the soil release has increased by around 12.9 Gtons C yr −1 . DOI: 10.1034/j.1600-0889.1996.t01-2-00001.x

The Cenozoic evolution of the strontium and carbon cycles: relative importance of continental erosion and mantle exchanges

The past variations of the seawater 87Sr 86Sr isotopic ratio are related to changes in the relative contribution of the mantle Sr input to the ocean and the Sr supply from continental weathering. Recently, it has been postulated that the Cenozoic increase in the seawater 87Sr 86Sr isotopic ratio was associated with the uplift of the Himalayan and Andean mountains at that time. These orogenies may have changed the Sr isotopic ratio of the continental rocks undergoing weathering (as a result of extensive metamorphism), increased the river flux of Sr through enhanced weathering in these regions and possibly caused the global climatic cooling trend of the Cenozoic. A model of the major geochemical cycles coupled to an energy balance climate model is used to explore the possible causes of the Mesozoic-Cenozoic fluctuations in the seawater 87Sr 86Sr isotopic ratio. The contribution of the mantle exchanges at mid-ocean ridges, of the recycling of seafloor carbonates through plate margin volcanism and of the alteration of seafloor basalts to the fluctuations of the seawater 87Sr 86Sr isotopic ratio are studied. Finally, this model tentatively describes the impact of the Himalayan orogeny on the geochemical cycles of Sr and C. Some possible effects of the extensive metamorphism associated with the India-Asia collision and of the Himalayan uplift are modelled. The model reproduces the Cenozoic increase of the seawater 87Sr 86Sr isotopic ratio. However, the impact of the Himalayan orogeny on the C cycle appears to be limited and insufficient to generate the global climatic cooling of the Cenozoic. Rather, in the model, the Cenozoic cooling is mostly due to the reduction of the CO 2 emission from mid-ocean ridge volcanism and to changes in the chemical weathering rates in the rest of the world excluding the Himalayas.