共查询到20条相似文献，搜索用时 125 毫秒
1.
The geographical distribution of the change in soil wetness in response to an increase in atmospheric carbon dioxide was investigated by using a mathematical model of climate. Responding to the increase in carbon dioxide, soil moisture in the model would be reduced in summer over extensive regions of the middle and high latitudes, such as the North American Great Plains, western Europe, northern Canada, and Siberia. These results were obtained from the model with predicted cloud cover and are qualitatively similar to the results from several numerical experiments conducted earlier with prescribed cloud cover. 相似文献
2.
Results obtained from a detailed air-sea-ice climate model for an instantaneous increase in the atmospheric carbon dioxide content are used to estimate the transient surface temperature response for several time-dependent carbon dioxide increase scenarios. The inclusion of realistic variations of land fraction and ocean mixing with latitude is found to limit the applicability of steady- state simulations as approximate guides to the actual time-dependent temperature response, particularly when the regional response is considered. 相似文献
3.
Meckler AN Clarkson MO Cobb KM Sodemann H Adkins JF 《Science (New York, N.Y.)》2012,336(6086):1301-1304
Records of atmospheric carbon dioxide concentration (P(CO(2))) and Antarctic temperature have revealed an intriguing change in the magnitude of interglacial warmth and P(CO(2)) at around 430,000 years ago (430 ka), but the global climate repercussions of this change remain elusive. Here, we present a stalagmite-based reconstruction of tropical West Pacific hydroclimate from 570 to 210 ka. The results suggest similar regional precipitation amounts across the four interglacials contained in the record, implying that tropical hydroclimate was insensitive to interglacial differences in P(CO(2)) and high-latitude temperature. In contrast, during glacial terminations, drying in the tropical West Pacific accompanied cooling events in northern high latitudes. Therefore, the tropical convective heat engine can either stabilize or amplify global climate change, depending on the nature of the climate forcing. 相似文献
4.
Joos F Plattner GK Stocker TF Marchal O Schmittner A 《Science (New York, N.Y.)》1999,284(5413):464-467
A low-order physical-biogeochemical climate model was used to project atmospheric carbon dioxide and global warming for scenarios developed by the Intergovernmental Panel on Climate Change. The North Atlantic thermohaline circulation weakens in all global warming simulations and collapses at high levels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, atmospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cycle compensate the reduction in downward mixing of anthropogenic carbon, except when the North Atlantic thermohaline circulation collapses. 相似文献
5.
Tierney JE Russell JM Huang Y Damsté JS Hopmans EC Cohen AS 《Science (New York, N.Y.)》2008,322(5899):252-255
The processes that control climate in the tropics are poorly understood. We applied compound-specific hydrogen isotopes (deltaD) and the TEX(86) (tetraether index of 86 carbon atoms) temperature proxy to sediment cores from Lake Tanganyika to independently reconstruct precipitation and temperature variations during the past 60,000 years. Tanganyika temperatures follow Northern Hemisphere insolation and indicate that warming in tropical southeast Africa during the last glacial termination began to increase approximately 3000 years before atmospheric carbon dioxide concentrations. deltaD data show that this region experienced abrupt changes in hydrology coeval with orbital and millennial-scale events recorded in Northern Hemisphere monsoonal climate records. This implies that precipitation in tropical southeast Africa is more strongly controlled by changes in Indian Ocean sea surface temperatures and the winter Indian monsoon than by migration of the Intertropical Convergence Zone. 相似文献
6.
Graham NE 《Science (New York, N.Y.)》1995,267(5198):666-671
Observations show that global average tropospheric temperatures have been rising during the past century, with the most recent portion of record showing a sharp rise since the mid-1970s. This study shows that the most recent portion of the global temperature record (1970 to 1992) can be closely reproduced by atmospheric models forced only with observed ocean surface temperatures. In agreement with a diverse suite of controversial observational evidence from the past 40 years, the upward trend in simulated tropospheric temperatures is caused by an enhancement of the tropical hydrologic cycle driven by increasing tropical ocean temperatures. Although it is possible that the observed behavior is due to natural climate variability, there is disquieting similarity between these model results, observed climate trends in recent decades, and the early expressions of the climatic response to increased atmospheric carbon dioxide in numerical simulations. 相似文献
7.
Idso SB 《Science (New York, N.Y.)》1980,207(4438):1462-1463
The mean global increase in thermal radiation received at the surface of the earth as a consequence of a doubling of the atmospheric carbon dioxide content is calculated to be 2.28 watts per square meter. Multiplying this forcing function by the atmosphere's surface air temperature response function, which has recently been determined by three independent experimental analyses to have a mean global value of 0.113 K per watt per square meter, yields a value of 相似文献
8.
A simple climate model has been used to calculate the effect of past changes in the land-sea distribution on the seasonal cycle of temperatures during the last 100 million years. Modeled summer temperatures decreased over Greenland by more than 10 degrees C and over Antarctica by 5 degrees to 8 degrees C. For the last 80 million years, this thermal response is comparable in magnitude to estimated atmospheric carbon dioxide effects. Analysis of paleontological data provides some support for the proposed hypothesis that large changes due to seasonality may have sometimes resulted in an ice-free state due to high summer temperature rather than year-round warmth. Such "cool" non-glacials may have prevailed for as much as one-third of the last 100 million years. 相似文献
9.
A neoproterozoic snowball earth 总被引：17，自引：0，他引：17
Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits in Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity in the surface ocean collapsed for millions of years. This collapse can be explained by a global glaciation (that is, a snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level. The rapid termination would have resulted in a warming of the snowball Earth to extreme greenhouse conditions. The transfer of atmospheric carbon dioxide to the ocean would result in the rapid precipitation of calcium carbonate in warm surface waters, producing the cap carbonate rocks observed globally. 相似文献
10.
A sea surface temperature (SST) record based on planktonic foraminiferal magnesium/calcium ratios from a site in the western equatorial Pacific warm pool reveals that glacial-interglacial oscillations in SST shifted from a period of 41,000 to 100,000 years at the mid-Pleistocene transition, 950,000 years before the present. SST changes at both periodicities were synchronous with eastern Pacific cold-tongue SSTs but preceded changes in continental ice volume. The timing and nature of tropical Pacific SST changes over the mid-Pleistocene transition implicate a shift in the periodicity of radiative forcing by atmospheric carbon dioxide as the cause of the switch in climate periodicities at this time. 相似文献
11.
Simulation of recent southern hemisphere climate change 总被引：4，自引：0，他引：4
Recent observations indicate that climate change over the high latitudes of the Southern Hemisphere is dominated by a strengthening of the circumpolar westerly flow that extends from the surface to the stratosphere. Here we demonstrate that the seasonality, structure, and amplitude of the observed climate trends are simulated in a state-of-the-art atmospheric model run with high vertical resolution that is forced solely by prescribed stratospheric ozone depletion. The results provide evidence that anthropogenic emissions of ozonedepleting gases have had a distinct impact on climate not only at stratospheric levels but at Earth's surface as well. 相似文献
12.
Measurements of the concentrations and carbon-13/carbon-12 isotope ratios of atmospheric carbon dioxide can be used to quantify the net removal of carbon dioxide from the atmosphere by the oceans and terrestrial plants. A study of weekly samples from a global network of 43 sites defined the latitudinal and temporal patterns of the two carbon sinks. A strong terrestrial biospheric sink was found in the temperate latitudes of the Northern Hemisphere in 1992 and 1993, the magnitude of which is roughly half that of the global fossil fuel burning emissions for those years. The challenge now is to identify those processes that would cause the terrestrial biosphere to absorb carbon dioxide in such large quantities. 相似文献
13.
Sprague AL Boynton WV Kerry KE Janes DM Hunten DM Kim KJ Reedy RC Metzger AE 《Science (New York, N.Y.)》2004,306(5700):1364-1367
The gamma ray spectrometer on the Mars Odyssey spacecraft measured an enhancement of atmospheric argon over southern high latitudes during autumn followed by dissipation during winter and spring. Argon does not freeze at temperatures normal for southern winter (approximately 145 kelvin) and is left in the atmosphere, enriched relative to carbon dioxide (CO2), as the southern seasonal cap of CO2 frost accumulates. Calculations of seasonal transport of argon into and out of southern high latitudes point to meridional (north-south) mixing throughout southern winter and spring. 相似文献
14.
Climate impact of increasing atmospheric carbon dioxide 总被引：2，自引：0，他引：2
Hansen J Johnson D Lacis A Lebedeff S Lee P Rind D Russell G 《Science (New York, N.Y.)》1981,213(4511):957-966
The global temperature rose by 0.2 degrees C between the middle 1960's and 1980, yielding a warming of 0.4 degrees C in the past century. This temperature increase is consistent with the calculated greenhouse effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean trend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980's. Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climatic zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage. 相似文献
15.
Martrat B Grimalt JO Shackleton NJ de Abreu L Hutterli MA Stocker TF 《Science (New York, N.Y.)》2007,317(5837):502-507
Centennial climate variability over the last ice age exhibits clear bipolar behavior. High-resolution analyses of marine sediment cores from the Iberian margin trace a number of associated changes simultaneously. Proxies of sea surface temperature and water mass distribution, as well as relative biomarker content, demonstrate that this typical north-south coupling was pervasive for the cold phases of climate during the past 420,000 years. Cold episodes after relatively warm and largely ice-free periods occurred when the predominance of deep water formation changed from northern to southern sources. These results reinforce the connection between rapid climate changes at Mediterranean latitudes and century-to-millennial variability in northern and southern polar regions. 相似文献
16.
The factors that determine climate response times were investigated with simple models and scaling statements. The response times are particularly sensitive to (i) the amount that the climate response is amplified by feedbacks and (ii) the representation of ocean mixing. If equilibrium climate sensitivity is 3 degrees C or greater for a doubling of the carbon dioxide concentration, then most of the expected warming attributable to trace gases added to the atmosphere by man probably has not yet occurred. This yet to be realized warming calls into question a policy of "wait and see" regarding the issue of how to deal with increasing atmospheric carbon dioxide and other trace gases. 相似文献
17.
Global cooling? 总被引：1，自引：0，他引：1
The world's inhabitants, including Scientists, live primarily in the Northern Hemisphere. It is quite natural to be concerned about events that occur close to home and neglect faraway events. Hence, it is not surprising that so little attention has been given to the Southern Hemisphere. Evidence for global cooling has been based, in large part, on a severe cooling trend at high northern latitudes. This article points out that the Northern Hemisphere cooling trend appears to be out of phase with a warming trend at high latitudes in the Southern Hemisphere. The data are scanty. We cannot be sure that these temperature fluctuations are be not the result of natural causes. How it seems most likely that human activity has already significantly perturbed the atmospheric weather system. The effect of particulate matter pollution should be most severe in the highly populated and industrialized Northern Hemisphere. Because of the rapid diffusion of CO(2) molecules within the atmosphere, both hemispheres will be subject to warming due to the atmospheric (greenhouse) effect as the CO(2) content of the atmosphere builds up from the combustion of fossil fuels. Because of the differential effects of the two major sources of atmospheric pollution, the CO(2) greenhouse effect warming trend should first become evident in the Southern Hemisphere. The socioeconomic and political consequences of climate change are profound. We need an early warning system such as would be provided by a more intensive international world weather watch, particularly at high northern and southern latitudes. 相似文献
18.
The Eocene greenhouse climate state has been linked to a more vigorous hydrologic cycle at mid- and high latitudes; similar information on precipitation levels at low latitudes is, however, limited. Oxygen isotopic fluxes track moisture fluxes and, thus, the δ(18)O values of ocean surface waters can provide insight into hydrologic cycle changes. The offset between tropical δ(18)O values from sampled Eocene sirenian tooth enamel and modern surface waters is greater than the expected 1.0 per mil increase due to increased continental ice volume. This increased offset could result from suppression of surface-water δ(18)O values by a tropical, annual moisture balance substantially wetter than that of today. Results from an atmospheric general circulation model support this interpretation and suggest that Eocene low latitudes were extremely wet. 相似文献
19.
20.
Reconstructions of ancient atmospheric carbon dioxide (CO2) variations help us better understand how the global carbon cycle and climate are linked. We compared CO2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO2 concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO2 concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO2 concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland. 相似文献