Lead–lag relationships between global mean temperature and the atmospheric CO<inf>2</inf> content in dependence of the type and time scale of the forcing

© 2016 Elsevier B.V.By employing an Earth system model of intermediate complexity (EMIC) developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), mutual lags between global mean surface air temperature, T and the atmospheric CO2 content, q, in dependence of the type and time scale of the external forcing are explored. In the simulation, which follows the protocol of the Coupled Models Intercomparison Project, phase 5, T leads q for volcanically-induced climate variations. In contrast, T lags behind q for changes caused by anthropogenic CO2 emissions into the atmosphere. In additional idealized numerical experiments, driven by periodic external emissions of carbon dioxide into the atmosphere, T always lags behind q as expected. In contrast, if the model is driven by the periodic non-greenhouse radiative forcing, T leads q for the external forcing time scale ≤4 ×102 yr, while q leads T at longer scales. The latter is an example that lagged correlations do not necessarily represent causal relationships in a system. This apparently counter-intuitive result, however, is a direct consequence of i) temperature sensitivity of the soil carbon stock (which decreases if climate is warmed and increases if climate is cooled), ii) conservation of total mass of carbon in the system in the absence of external carbon emissions, iii) increased importance of the oceanic branch of the carbon cycle at longer time scales. The results obtained with an EMIC are further interpreted with a conceptual Earth system model consisting of an energy balance climate model and a globally averaged carbon cycle model. The obtained results have implications to the empirical studies attempting to understand the origins of the contemporary climate change by applying lead–lag relationships to empirical data

Lead–lag relationships between global mean temperature and the atmospheric CO<inf>2</inf> content in dependence of the type and time scale of the forcing

© 2016 Elsevier B.V.By employing an Earth system model of intermediate complexity (EMIC) developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), mutual lags between global mean surface air temperature, T and the atmospheric CO2 content, q, in dependence of the type and time scale of the external forcing are explored. In the simulation, which follows the protocol of the Coupled Models Intercomparison Project, phase 5, T leads q for volcanically-induced climate variations. In contrast, T lags behind q for changes caused by anthropogenic CO2 emissions into the atmosphere. In additional idealized numerical experiments, driven by periodic external emissions of carbon dioxide into the atmosphere, T always lags behind q as expected. In contrast, if the model is driven by the periodic non-greenhouse radiative forcing, T leads q for the external forcing time scale ≤4 ×102 yr, while q leads T at longer scales. The latter is an example that lagged correlations do not necessarily represent causal relationships in a system. This apparently counter-intuitive result, however, is a direct consequence of i) temperature sensitivity of the soil carbon stock (which decreases if climate is warmed and increases if climate is cooled), ii) conservation of total mass of carbon in the system in the absence of external carbon emissions, iii) increased importance of the oceanic branch of the carbon cycle at longer time scales. The results obtained with an EMIC are further interpreted with a conceptual Earth system model consisting of an energy balance climate model and a globally averaged carbon cycle model. The obtained results have implications to the empirical studies attempting to understand the origins of the contemporary climate change by applying lead–lag relationships to empirical data

Lead–lag relationships between global mean temperature and the atmospheric CO<inf>2</inf> content in dependence of the type and time scale of the forcing

© 2016 Elsevier B.V.By employing an Earth system model of intermediate complexity (EMIC) developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), mutual lags between global mean surface air temperature, T and the atmospheric CO2 content, q, in dependence of the type and time scale of the external forcing are explored. In the simulation, which follows the protocol of the Coupled Models Intercomparison Project, phase 5, T leads q for volcanically-induced climate variations. In contrast, T lags behind q for changes caused by anthropogenic CO2 emissions into the atmosphere. In additional idealized numerical experiments, driven by periodic external emissions of carbon dioxide into the atmosphere, T always lags behind q as expected. In contrast, if the model is driven by the periodic non-greenhouse radiative forcing, T leads q for the external forcing time scale ≤4 ×102 yr, while q leads T at longer scales. The latter is an example that lagged correlations do not necessarily represent causal relationships in a system. This apparently counter-intuitive result, however, is a direct consequence of i) temperature sensitivity of the soil carbon stock (which decreases if climate is warmed and increases if climate is cooled), ii) conservation of total mass of carbon in the system in the absence of external carbon emissions, iii) increased importance of the oceanic branch of the carbon cycle at longer time scales. The results obtained with an EMIC are further interpreted with a conceptual Earth system model consisting of an energy balance climate model and a globally averaged carbon cycle model. The obtained results have implications to the empirical studies attempting to understand the origins of the contemporary climate change by applying lead–lag relationships to empirical data

Lead–lag relationships between global mean temperature and the atmospheric CO<inf>2</inf> content in dependence of the type and time scale of the forcing

© 2016 Elsevier B.V.By employing an Earth system model of intermediate complexity (EMIC) developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), mutual lags between global mean surface air temperature, T and the atmospheric CO2 content, q, in dependence of the type and time scale of the external forcing are explored. In the simulation, which follows the protocol of the Coupled Models Intercomparison Project, phase 5, T leads q for volcanically-induced climate variations. In contrast, T lags behind q for changes caused by anthropogenic CO2 emissions into the atmosphere. In additional idealized numerical experiments, driven by periodic external emissions of carbon dioxide into the atmosphere, T always lags behind q as expected. In contrast, if the model is driven by the periodic non-greenhouse radiative forcing, T leads q for the external forcing time scale ≤4 ×102 yr, while q leads T at longer scales. The latter is an example that lagged correlations do not necessarily represent causal relationships in a system. This apparently counter-intuitive result, however, is a direct consequence of i) temperature sensitivity of the soil carbon stock (which decreases if climate is warmed and increases if climate is cooled), ii) conservation of total mass of carbon in the system in the absence of external carbon emissions, iii) increased importance of the oceanic branch of the carbon cycle at longer time scales. The results obtained with an EMIC are further interpreted with a conceptual Earth system model consisting of an energy balance climate model and a globally averaged carbon cycle model. The obtained results have implications to the empirical studies attempting to understand the origins of the contemporary climate change by applying lead–lag relationships to empirical data

Phase Shift between Changes in Global Temperature and Atmospheric CO<inf>2</inf> Content under External Emissions of Greenhouse Gases into the Atmosphere

© 2019, Pleiades Publishing, Ltd. Abstract: The phase shift between changes in the global surface temperature Tg and atmospheric CO2 content (Formula Presented.) has been shown earlier not to characterize causal relationships in the Earth system in the general case. Specifically, the sign of this phase shift under nongreenhouse radiative forcing changes depends on the time scale of this forcing. This paper analyzes the phase shift between changes in the global surface temperature Tg and the atmospheric CO2 content (Formula Presented.) under synchronous external emissions of carbon dioxide and methane into the atmosphere on the basis of numerical experiments with the IAP RAS climatic model and a conceptual climate model with carbon cycle. For a sufficiently large time scale of external forcing, the changes in (Formula Presented.) lag relative to the corresponding changes in Tg

Time lag between changes in global temperature and atmospheric CO2 content under anthropogenic emissions of CO2 and CH4 into the atmosphere

© Published under licence by IOP Publishing Ltd. Previously, it was shown that the time lag between changes in global temperature T and atmospheric CO2 content q CO2 generally does not characterize cause-and-effect relationships in the Earth system. In particular, in the case of non-greenhouse radiative forcing the sign of this lag depends on the time scale of the forcing. In this paper, the time lag between changes in T and q CO2 under the external emissions of CO2 and CH4 into the atmosphere is studied. It was found that if the time scale of external emissions is large enough changes in q CO2 are lagging the corresponding changes in T, though the former is the main cause of the latter

Time lag between changes in global temperature and atmospheric CO2 content under anthropogenic emissions of CO2 and CH4 into the atmosphere

© Published under licence by IOP Publishing Ltd. Previously, it was shown that the time lag between changes in global temperature T and atmospheric CO2 content q CO2 generally does not characterize cause-and-effect relationships in the Earth system. In particular, in the case of non-greenhouse radiative forcing the sign of this lag depends on the time scale of the forcing. In this paper, the time lag between changes in T and q CO2 under the external emissions of CO2 and CH4 into the atmosphere is studied. It was found that if the time scale of external emissions is large enough changes in q CO2 are lagging the corresponding changes in T, though the former is the main cause of the latter

Phase Shift between Changes in Global Temperature and Atmospheric CO<inf>2</inf> Content under External Emissions of Greenhouse Gases into the Atmosphere

© 2019, Pleiades Publishing, Ltd. Abstract: The phase shift between changes in the global surface temperature Tg and atmospheric CO2 content (Formula Presented.) has been shown earlier not to characterize causal relationships in the Earth system in the general case. Specifically, the sign of this phase shift under nongreenhouse radiative forcing changes depends on the time scale of this forcing. This paper analyzes the phase shift between changes in the global surface temperature Tg and the atmospheric CO2 content (Formula Presented.) under synchronous external emissions of carbon dioxide and methane into the atmosphere on the basis of numerical experiments with the IAP RAS climatic model and a conceptual climate model with carbon cycle. For a sufficiently large time scale of external forcing, the changes in (Formula Presented.) lag relative to the corresponding changes in Tg

Linkages between Arctic and Mid-Latitude Weather and Climate: Unraveling the Impact of Changing Sea Ice and Sea Surface Temperatures during Winter

The study addresses the question, if observed changes in terms of Arctic-midlatitude linkages during winter are driven by Arctic Sea ice decline alone or if the increase of global sea surface temperatures plays an additional role. We compare atmosphere-only model experiments with ECHAM6 to ERA-Interim Reanalysis data. The model sensitivity experiment is implemented as a set of four combinations of sea ice and sea surface temperature boundary conditions. Atmospheric circulation regimes are determined and evaluated in terms of their cyclone and blocking characteristics and changes in frequency during winter. As a prerequisite, ECHAM6 reproduces general features of circulation regimes very well. Tropospheric changes induced by the change of boundary conditions are revealed and further impacts on the large-scale circulation up into the stratosphere are investigated. In early winter, the observed increase of atmospheric blocking in the region between Scandinavia and the Urals are primarily related to the changes in sea surface temperatures. During late winter, we find a weakened polar stratospheric vortex in the reanalysis that further impacts the troposphere. In the model sensitivity study a climatologically weakened polar vortex occurs only if sea ice is reduced and sea surface temperatures are increased together. This response is delayed compared to the reanalysis. The tropospheric response during late winter is inconclusive in the model, which is potentially related to the weak and delayed response in the stratosphere. The model experiments do not reproduce the connection between early and late winter as interpreted from the reanalysis. Potentially explaining this mismatch, we identify a discrepancy of ECHAM6 to reproduce the weakening of the stratospheric polar vortex through blocking induced upward propagation of planetary waves

Original Russian Text ©

Determination of the role of natural and anthropo genic factors in the modern climate change is one of the key problems of the 21st century. The objective of this work is to estimate the degree of the cause and effect correlations in the Earth system (ES) that can be judged from the time shifts in the time series of data, in particular, in the data on the temperature and СО 2 concentration in the atmosphere. The data of ice cores used to reconstruct climate changes in the Pleistocene, in particular, the glacia tion cycles, reveal a general time lag of the carbon dioxide concentration in the atmosphere q relative to the variations in the surface temperature T (see, for example, Frequently, the general lag of q relative to T revealed from the paleo data is an argument against the statement that the modern global warming is caused by the greenhouse effect of the anthropogenic increase in q. The lag of q relative to T was found in It is worth noting that glaciation cycles are related to variations in the parameters of the Earth&apos;s orbit (the so called Milankovitch cycles) with characteristic peri ods of approximately 100 000, 40 000, and 20 000 years. Climate changes (in particular, the temperature) occur due to variations in the orbit, and the tempera ture variations facilitate the variations in the concen tration of greenhouse gases in the atmosphere. The latter, in turn, influences the temperature variations. A similar effect can be also manifested if caused by the other radiative components. Variations in the СО 2 concentration in the atmo sphere can also occur due to the variations in the solu bility of the gas in seawater caused by temperature variations. During warm periods, СО 2 is released into the atmosphere from the ocean. In this relation, the increase in the СО 2 concentration in the atmosphere is sometimes interpreted as a consequence but not a cause of global warming occurring. In this work we show that the found mutual lags between the variations in the temperature and carbon dioxide concentrations in the atmosphere do not con tradict the conclusions that the key role in the modern climate changes belongs to the anthropogenic green house effect We consider a globally average climate model with the carbon cycle, which takes into account the gener ally accepted influence mechanisms of radiative per turbing forcing (including the greenhouse one) on the climate state and the interaction between the climate and the carbon cycle: = F land , Here, q is the deviation of the CО 2 concentration in the atmosphere from the initial (preindustrial) value q 0 = 590 Gt of C (which corresponds to a concentra tion of 278 ppm); D is the corresponding deviation of carbon resources in the ocean; M b and M s are the devi ations of carbon stocks in the vegetation and soil, respectively; T is the temperature deviation; E(t) are external (including anthropogenic) CО 2 emissions into the atmosphere; F oc is the CО 2 flux from the atmo sphere to the ocean; F land is the CО 2 flux from the atmo sphere to the terrestrial ecosystems; C = 10 9 J m -2