Changes in Earth's temperature have significant impacts on the global carbon cycle that vary at different time scales, yet to quantify such impacts with a simple scheme is traditionally deemed difficult. Here, we show that, by incorporating a temperature sensitivity parameter(1.64 ppm yr~(-1) ?C~(-1)) into a simple linear carbon-cycle model, we can accurately characterize the dynamic responses of atmospheric carbon dioxide(CO_2) concentration to anthropogenic carbon emissions and global temperature changes between 1850 and 2010(r~2 0.96 and the root-mean-square error 1 ppm for the period from 1960onward). Analytical analysis also indicates that the multiplication of the parameter with the response time of the atmospheric carbon reservoir(~12 year) approximates the long-term temperature sensitivity of global atmospheric CO_2concentration(~15 ppm?C~(-1)), generally consistent with previous estimates based on reconstructed CO_2 and climate records over the Little Ice Age. Our results suggest that recent increases in global surface temperatures, which accelerate the release of carbon from the surface reservoirs into the atmosphere, have partially offset surface carbon uptakes enhanced by the elevated atmospheric CO_2 concentration and slowed the net rate of atmospheric CO_2 sequestration by global land and oceans by ~30%since the 1960 s. The linear modeling framework outlined in this paper thus provides a useful tool to diagnose the observed atmospheric CO_2 dynamics and monitor their future changes. 相似文献
The Gulf of Guinea in the equatorial Atlantic is characterized by the presence of strong subsidence at certain times of the year. This subsidence appears in June and becomes well established from July to September. Since much of theWest African monsoon flow originates over the Gulf, Guinean subsidence is important for determining moisture sources for the monsoon. Using reanalysis products, I contribute to a physical understanding of what causes this seasonal subsidence, and how it relates to precipitation distributions across West Africa.There is a seasonal zonal overturning circulation above the Congo basin and the Gulf of Guinea in the ERA-Interim, ERA-40, NCEP2, and MERRA reanalyses. The up-branch is located in the Congo basin around 20°E. Mid-tropospheric easterly flows constitute the returning-branch and sinking over the Gulf of Guinea forms the down-branch, which diverges at 2°W near the surface, with winds to the east flowing eastward to complete the circulation. This circulation is driven by surface temperature differences between the eastern Gulf and Congo basin. Land temperatures remain almost uniform, around 298 K, throughout a year, but the Guinean temperatures cool rapidly from 294 K in May to about 290 K in August. These temperature changes increase the ocean/land temperature contrast, up to 8 K, and drive the circulation.I hypothesize that when the overturning circulation is anomalously strong, the northward moisture transport and Sahelian precipitation are also strong. This hypothesis is supported by ERA-Interim and PERSIANN-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record) data. 相似文献
This study simulates the effective radiative forcing(ERF) of tropospheric ozone from 1850 to 2013 and its effects on global climate using an aerosol–climate coupled model, BCC AGCM2.0.1 CUACE/Aero, in combination with OMI(Ozone Monitoring Instrument) satellite ozone data. According to the OMI observations, the global annual mean tropospheric column ozone(TCO) was 33.9 DU in 2013, and the largest TCO was distributed in the belts between 30°N and 45°N and at approximately 30°S; the annual mean TCO was higher in the Northern Hemisphere than that in the Southern Hemisphere;and in boreal summer and autumn, the global mean TCO was higher than in winter and spring. The simulated ERF due to the change in tropospheric ozone concentration from 1850 to 2013 was 0.46 W m~(-2), thereby causing an increase in the global annual mean surface temperature by 0.36℃, and precipitation by 0.02 mm d~(-1)(the increase of surface temperature had a significance level above 95%). The surface temperature was increased more obviously over the high latitudes in both hemispheres, with the maximum exceeding 1.4?C in Siberia. There were opposite changes in precipitation near the equator,with an increase of 0.5 mm d~(-1)near the Hawaiian Islands and a decrease of about-0.6 mm d~(-1)near the middle of the Indian Ocean. 相似文献
We evaluate the capacity of a regional climate model to represent observed extreme temperature and precipitation events and also examine the impact of increased resolution, in an effort to identify added value in this respect. Two climate simulations of western Canada (WCan) were conducted with the Canadian Regional Climate Model (version 4) at 15 (CRCM15) and 45?km (CRCM45) horizontal resolution driven at the lateral boundaries by data from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA-40) for the period 1973–1995. The simulations were evaluated using the spline-interpolated dataset ANUSPLIN, a daily observational gridded surface temperature and precipitation product with a nominal resolution of approximately 10?km. We examine a range of climate extremes, comprising the 10th and 90th percentiles of daily maximum (TX) and minimum (TN) temperatures, the 90th percentile of daily precipitation (PR90), and the 27 core Climate Daily Extremes (CLIMDEX) indices.Both simulations exhibit cold biases compared with observations over WCan, with the bias exacerbated at higher resolution, suggesting little added value for temperature overall. There are instances, however, of regional improvement in the spatial pattern of temperature extremes at the higher resolution of CRCM15 (e.g., the CLIMDEX index for the annual number of days when TX?>?25°C). The high-resolution simulations also reveal similarly localized features in precipitation (e.g., rain shadows) that are not resolved at the 45?km resolution. With regard to precipitation extremes, although both simulations generally display wet biases, CRCM15 features a reduced bias in PR90 in all seasons except winter. This improvement occurs despite the fact that spatial and interannual variability of PR90 in CRCM15 is significantly overestimated relative to both CRCM45 and ANUSPLIN. We posit that these characteristics are the result of demonstrable differences between corresponding topographical datasets used in the gridded observations and CRCM, the resulting errors propagated to physical variables tied to elevation and the beneficial effect of subsequent spatial averaging. Because topographical input is often discordant between simulations and gridded observations, it is argued that a limited form of spatial averaging may contribute added value beyond that which has already been noted in previous studies with respect to small-scale climate variability. 相似文献
India's growing role in the global climate debate makes it imperative to analyse emission reduction policies and strategies across a range of GHGs, especially for under-researched non-CO2 gases. Hydrofluorocarbons' (HFCs) usage in cooling equipment and subsequent emissions are expected to increase dramatically in India with the phase-out of hydrochlorofluorocarbons (HCFCs) as coolants in air-conditioning equipment. We focus on the residential air-conditioning sector in India and analyse a suite of HFC and alternative coolant gas scenarios for understanding the implications for GHG emissions from this sector within an integrated assessment modelling framework. We find that, if unabated, HFC410A emissions will contribute to 36% of the total global warming impact from the residential air-conditioner sector in India in 2050, irrespective of the future economic growth trajectory, and the remaining 64% is from energy to power residential air-conditioners. A move towards more efficient, low global warming potential (GWP) alternative refrigerants will significantly reduce the cumulative global warming footprint of this sector by 37% during the period 2010–2050, due to gains both from energy efficiency as well as low GWP alternatives. Best practices for reducing direct emissions are important, but only of limited utility, and if a sustainable lifestyle is adopted by consumers with lower floorspace, low GWP refrigerants, and higher building envelope efficiencies, cumulative emissions during 2010–2050 can be reduced by 46% compared to the Reference scenario.
Policy relevance
Our analysis has important implications for Indian climate policy. We highlight that the Indian government's amendment proposal to the Montreal Protocol is a strong signal to the Indian market that the transition away from high GWP refrigerants towards low/zero GWP alternatives will happen sooner or later. The Bureau of Energy Efficiency should extend building energy conservation code policy to residential buildings immediately, and the government should mandate it. Government authorities should set guidelines and mandate reporting of data related to air-conditioner coolant recharge frequency and recovery of scrapped air-conditioner units. For contentious issues like flammability where there is no consensus within the industry, the government needs to undertake an independent technical assessment that can provide unbiased and reliable information to the market. 相似文献