Global Mean Annual Temperature Research Articles

The biogeophysical climatic impacts of anthropogenic land use change during the Holocene

Abstract. The first agricultural societies were established around 10 ka BP and had spread across much of Europe and southern Asia by 5.5 ka BP with resultant anthropogenic deforestation for crop and pasture land. Various studies (e.g. Joos et al., 2004; Kaplan et al., 2011; Mitchell et al., 2013) have attempted to assess the biogeochemical implications for Holocene climate in terms of increased carbon dioxide and methane emissions. However, less work has been done to examine the biogeophysical impacts of this early land use change. In this study, global climate model simulations with Hadley Centre Coupled Model version 3 (HadCM3) were used to examine the biogeophysical effects of Holocene land cover change on climate, both globally and regionally, from the early Holocene (8 ka BP) to the early industrial era (1850 CE). Two experiments were performed with alternative descriptions of past vegetation: (i) one in which potential natural vegetation was simulated by Top-down Representation of Interactive Foliage and Flora Including Dynamics (TRIFFID) but without land use changes and (ii) one where the anthropogenic land use model Kaplan and Krumhardt 2010 (KK10; Kaplan et al., 2009, 2011) was used to set the HadCM3 crop regions. Snapshot simulations were run at 1000-year intervals to examine when the first signature of anthropogenic climate change can be detected both regionally, in the areas of land use change, and globally. Results from our model simulations indicate that in regions of early land disturbance such as Europe and south-east Asia detectable temperature changes, outside the normal range of variability, are encountered in the model as early as 7 ka BP in the June–July–August (JJA) season and throughout the entire annual cycle by 2–3 ka BP. Areas outside the regions of land disturbance are also affected, with virtually the whole globe experiencing significant temperature changes (predominantly cooling) by the early industrial period. The global annual mean temperature anomalies found in our single model simulations were −0.22 at 1850 CE, −0.11 at 2 ka BP, and −0.03 °C at 7 ka BP. Regionally, the largest temperature changes were in Europe with anomalies of −0.83 at 1850 CE, −0.58 at 2 ka BP, and −0.24 °C at 7 ka BP. Large-scale precipitation features such as the Indian monsoon, the Intertropical Convergence Zone (ITCZ), and the North Atlantic storm track are also impacted by local land use and remote teleconnections. We investigated how advection by surface winds, mean sea level pressure (MSLP) anomalies, and tropospheric stationary wave train disturbances in the mid- to high latitudes led to remote teleconnections.

Global and Mediterranean climate change: a short summary.

Regional climate changes impact health and ecosystems, creating new risks, determined not only by weather events, but also by changing exposures and vulnerabilities. These issues, and in particular those regarding occupational safety, have not been sufficiently addressed to date.

The Origin and Development of the Central European Man-made Landscape, Habitat and Species Diversity as Affected by Climate and its Changes – a Review

The Origin and Development of the Central European Man-made Landscape, Habitat and Species Diversity as Affected by Climate and its Changes – a Review

Reconstructing the paleohydrology of a cretaceous Alaskan paleopolar coastal plain from stable isotopes of bivalves

As global mean annual temperatures continue to rise, modern Arctic climates are changing at an incredibly fast rate. To predict changing climate dynamics, a number of researchers have been focused on characterizing Arctic climate from ancient greenhouse worlds such as the Cretaceous and Eocene. Characterization of these climates requires analysis of a variety of proxy materials. Here we use bivalve shells, identified as Nucula aff. Nucula percrassa Conrad, from the Cretaceous (early Maastrichtian) Prince Creek Formation in combination with isotope data from previous lithologic and isotopic studies to characterize a cool-house Cretaceous climate bounded by greenhouse climates (mid-Cretaceous thermal maximum and Late Paleocene climate). Bivalves were analyzed by powder X-ray diffraction (PXRD), cathodoluminescence (CL), and thin section petrography to determine mineralogy and integrity of shells. PXRD analysis indicates that shells are composed of primary aragonite and not secondary calcite. Thin section and CL images reveal well preserved shell morphology including daily growth lines, and no luminescent patches or coarsening of crystal sizes to indicate diagenetic alteration/recrystallization. Aragonite carbon isotopic composition (δ13Carag) range from +0.45‰ to −3.00‰ VPDB and average −1.58‰. Aragonite oxygen isotopic composition (δ18Oarag) range from −10.48‰ to −15.42‰ VPDB and average −12.83‰. Using temperatures from 4.5°C to 12.5°C, the salinity–δ18Owater relationship of a modern Arctic setting from Torres et al. (2011), and the water–aragonite equation of Grossman and Ku (1986) reveal salinity ranges between 8 and 17.7ppt. Using these salinity ranges and temperatures, N. percrassa precipitated shell aragonite from water that ranged between δ18Owater=−14.41‰ VSMOW (at 12.5°C) and −16.23‰ (at 4.5°C). Shell growth was in equilibrium with water that represents a coastal, mixed water setting such as an estuary. When combined with previous studies, the mixture of fresh:marine water represents a 50%:50% to 72%:28% mixture and ranged between −14.41‰ and −16.23‰ during spring to summer months.

Estimation of late Eocene (Bartonian–Priabonian) terrestrial palaeoclimate: Contributions from megafloral assemblages from central Germany

Abstract The Eocene, the world’s last global greenhouse period, shows distinct climatic developments through time, from subtropical towards warm-temperate conditions in Europe. The present paper investigates the response of five floras of the central German Weiselster Basin from different stratigraphic ages to terrestrial palaeoclimatic variations. The floras were selected from the Zeitz Floral Assemblage (“Florenkomplex”) and cover a time interval of ca. 3.5 Myr within the late Eocene, which is supposed to be a period of gradual decline of global mean annual temperatures. The Zeitz Floral Assemblage was characterized by mainly evergreen, notophyllous intrazonal vegetation, consisting of subtropical and warm-temperate elements. The five floras as well as the entire Zeitz Floral Assemblage have been analysed using the following quantitative techniques: leaf margin analysis (LMA), Climate Leaf Analysis Multivariate Program (CLAMP) and Coexistence Approach (CA). Furthermore, the results have been compared with previously published estimates for additional localities from the same area and age. The temperature estimates derived for the Zeitz Floral Assemblage are in a good agreement with those of previous studies i.e. mean annual temperature (MAT) 16.1–20.0 °C, warmest month mean temperature (WMMT) 24.9–26.4 °C, coldest month mean temperature (CMMT) 9.2–13.3 °C. Deviations have been determined for the calculated mean annual precipitation (MAP 1308–1335 mm) compared to previously published data, indicating values of about 2000 mm. Both CLAMP and CA reveal clear hints for seasonality in precipitation which is in agreement with previous phytosociological assumptions and palynological data. The estimates for the individual sites differ between the different techniques as well as among the individual sites, but generally indicate no temporal trends in temperature and precipitation development. Additionally, the applicability of these techniques for fluvial-estuarine plant assemblages, as well as the applicability of intrazonal vegetation for reconstructing transregional climate conditions are discussed. Taphonomic and methodical biases are also subject of debate.

‘Study the past, if you would divine the future’: a retrospective on measuring and understanding Quaternary climate change

ABSTRACTResearch on Quaternary climate change is reviewed from the perspective of the real or potential contribution to improving our ability to predict the climate of the future. For convenience the literature is divided into four timescales: orbital, sub‐Milankovitch, Holocene and the last 2000 years. Four ‘challenges’ provide a framework for discussion: better understanding of the way the climate system works, better forecasting of the drivers of climate change, improved estimates of climate sensitivity (change in global mean annual temperature per unit increase in forcing) and evaluation of the models used to predict the climate of the future. Although a great deal of progress has been made, it is concluded that there are some aspects of our scientific culture that limit our potential. These include our tradition of storytelling rather than critical hypothesis testing, an over‐emphasis on the role of surface water sinking in the far north Atlantic as a driver of ocean circulation and an attendant under‐emphasis on the critical importance of changes in atmospheric circulation, and a lack of rigour in testing the hypothesis that changes in solar irradiance are an important driver of climate change.

Effects of regional afforestation on global climate

Carbon (C) sequestration following afforestation is regarded as economically, politically, and technically feasible for fighting global warming, whereas the afforested area which will contribute more efficiently as sinks for CO2 is still uncertain. To compare the benefits for C sequestration combined with its biogeochemical effects, an earth system model of intermediate complexity, the McGill Paleoclimate Model-2 (MPM-2) is used to identify the biogeophysical effects of regional afforestation on shaping global climate. An increase in forest in China has led to a prominent global warming during summer around 45° N. Conversely, the forest expansion in the USA causes a noticeable increase in global mean annual temperature during winter. Afforestation in the USA and China brings about a decrease in annual mean meridional oceanic heat transport, while the afforestation in low latitudes of the southern hemisphere causes an increase. These local and global impacts suggest that regional tree plantations may produce a differential effect on the Earth's climate, and even exert an opposite effect on the annual mean meridional oceanic heat transport; they imply that its spatial variation of biogeophysical feedbacks needs to be considered when evaluating the benefits of afforestation.

Assessing orbitally-forced interglacial climate variability during the mid-Pliocene Warm Period

The traditional view of the Pliocene is one of an epoch with higher than present global mean annual temperatures (∼2 to 3 °C) and stable climate conditions. Published data-model comparisons for the mid-Pliocene Warm Period (mPWP: ∼3.3 to 3 million years ago) have identified specific regions of concordance and discord between climate model outputs and marine/terrestrial proxy data. Due to the time averaged nature of global palaeoenvironmental syntheses, it has been hypothesised that climate variability during interglacial events within the mPWP could contribute to site-specific data/model disagreement. The Hadley Centre Coupled Climate Model Version 3 (HadCM3) is used to assess the nature of climate variability around two interglacial events within the mPWP that have different characteristics of orbital forcing (Marine Isotope Stages KM5c and K1). Model results indicate that ±20 kyr on either side of the MIS KM5c, orbital forcing produced a less than 1 °C change in global mean annual temperatures. Regionally, mean annual surface air temperature (SAT) variability can reach 2 to 3 °C. Seasonal variations exceed those predicted for the annual mean and can locally exceed 5 °C. Simulations 20 kyr on either side of MIS K1 show considerably increased variability in relation to KM5c.We demonstrate that orbitally-forced changes in surface air temperature during interglacial events within the mPWP can be substantial, and could therefore contribute to data/model discord. This is especially likely if proxies preserve growing season rather than mean annual temperatures.Model results indicate that peak MIS KM5c and K1 interglacial temperatures were not globally synchronous, highlighting leads and lags in temperature in different regions. This highlights the potential pitfalls in aligning peaks in proxy-derived temperatures across geographically diverse data sites, and indicates that a single climate model simulation for an interglacial event is inadequate to capture peak temperature change in all regions.We conclude that the premise of sustained global warmth and stable Pliocene climate conditions is incomplete. We also contend that the likely nature of Pliocene interglacial climate variability is more akin to interglacial events within the Quaternary, where the character of interglacials is known to be diverse. In the future, the utility of Pliocene data/model comparisons is dependent upon 1) establishing precise chronology of the proxy data, 2) providing climate models with fully proxy-consistent boundary conditions and 3) in utilising ensembles of climate simulations that can adequately capture orbital variability around any studied interval.

The climatic effects of modifying cirrus clouds in a climate engineering framework

AbstractThe climatic effects of climate engineering—or geoengineering—via cirrus cloud thinning are examined. Thinner cirrus clouds can allow more outgoing longwave radiation to escape to space, potentially cooling the climate. The cloud properties and climatic effects due to perturbing the ice crystal fall speed are investigated in a set of hemispheric scale sensitivity experiments with the Community Earth System Model. It is found that increasing the ice crystal fall speed, as an analog to cirrus cloud seeding, depletes high‐level clouds and reduces the longwave cloud forcing. Deliberate depletion of cirrus clouds increases outgoing longwave radiation, reduces the upper tropospheric water vapor, and cools the climate. Global cirrus cloud thinning gave a net cloud forcing change of −1.55 W m−2 and a global annual mean temperature change of −0.94 K. Though there is negligible change in the global annual mean precipitation (−0.001 mm/d), the spatially nonhomogeneous forcing induces circulation changes and hence remote climate changes. Climate engineering the Southern Hemisphere only results in a northward shift of the Intertropical Convergence Zone and possible Sahelian drought alleviation, while targeting the Northern Hemisphere alone causes a greater cooling. It was found that targeting cirrus clouds everywhere outside of the tropics results in changes to the circulation and precipitation even in the nonclimate engineered regions, underscoring the risks of remote side effects and indeed the complexity of the climate system.

The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1

Abstract. The mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of close-to-modern CO2 concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean to simulate this warm period, incorporating recent Miocene CO2 reconstructions of 400 ppm (parts per million). We simulate a global mean annual temperature (MAT) of 18 °C, ~4 °C above the preindustrial value, but 4 °C colder than the global Miocene MAT we calculate from climate proxies. Sensitivity tests reveal that the inclusion of a reduced Antarctic ice sheet, an equatorial Pacific temperature gradient characteristic of a permanent El Niño, increased CO2 to 560 ppm, and variations in obliquity only marginally improve model–data agreement. All MMCO simulations have an Equator to pole temperature gradient that is at least ~10 °C larger than that reconstructed from proxies. The MMCO simulation most comparable to the proxy records requires a CO2 concentration of 800 ppm. Our results illustrate that MMCO warmth is not reproducible using the CESM1.0 forced with CO2 concentrations reconstructed for the Miocene or including various proposed Earth system feedbacks; the remaining discrepancy in the MAT is comparable to that introduced by a CO2 doubling. The model's tendency to underestimate proxy derived global MAT and overestimate the Equator to pole temperature gradient suggests a major climate problem in the MMCO akin to those in the Eocene. Our results imply that this latest model, as with previous generations of climate models, is either not sensitive enough or additional forcings remain missing that explain half of the anomalous warmth and pronounced polar amplification of the MMCO.

A new stable isotope record of Neogene paleoenvironments and mammalian paleoecologies in the western Great Plains during the expansion of C4 grasslands

Stable isotopes in horse teeth from the North American Great Plains show that equids began to incorporate C4 plants in their diets about 6.5million years ago as C4 grasslands expanded. However, the ecological response of many other ungulates to this expansion is poorly documented. We use stable carbon isotopes in mammalian tooth enamel to test whether other ungulates adapted by incorporating C4 vegetation in their diets. The openness of habitats before the expansion of C4 grasslands is uncertain, with plant phytolith studies suggesting a patchy environment with open-habitat grasses and forest, and pollen and macrofloral studies suggesting more forested habitats. To address this problem we use a model that predicts carbon isotope values for tooth enamel for a variety of environments, based on values in modern plants. Carbon and oxygen isotopes were analyzed in medium to large herbivores from three late Miocene and three Pliocene local faunas comprising a total of 13 and 7 genera, respectively, and 59 and 42 individuals. Results indicate that before the expansion of C4 grasslands, taxa with high-crowned teeth were consuming predominantly C3 vegetation. In contrast, by the late Pliocene most taxa studied were consuming a component of C4 vegetation and only the peccary Platygonus sp. had a pure C3 diet. C4 consumption increased in the late Pliocene (~3.0Ma) Big Springs local fauna probably in response to increased C4 biomass. Most landscapes in the late Miocene of Nebraska were open, such as woodland-savanna or C3 grassland, although low carbon values from the Pratt Slide local fauna suggest a denser, presumably forested area. This general pattern suggests an expansion of open-habitats no later than 12Ma (early Clarendonian). Through the Miocene–Pliocene transition there was an overall shift to lower δ18O enamel values, which parallels the long-term decrease in global mean annual temperature inferred from the marine record. Our results indicate that major changes in the diets of medium and large herbivores broadly corresponded with increased C4 biomass and cooling climate from the latest Miocene to the late Pliocene.

Effect of Elevated Temperature on Development Time of Rice Yellow Stem Borer

Insects, as cold-blooded animals are directly under the control of temperature for their growth and they cannot sustain living below and above certain thresholds. Therefore, temperature is probably the single most important environmental factor influencing insect behavior. Current estimates of changes in climate indicate an increase in global mean annual temperatures of 1°C by 2025 and 3°C by the end of the next century. Such increases in temperature may decrease the developmental time and increase the number of generations per year. An investigation was adopted to understand the effect of five different constant temperatures (28.3°C, 30.6°C, 32.7°C, 34.3°C and 36°C) on the development time of Yellow Stem Borer (YSB). The results revealed that the number of eggs laid by YSB increased at higher temperatures while egg hatching was reduced. Egg hatching was higher (90.6%) in 30.6°C followed by 28.3°C. The development time taken by different stages of the YSB revealed that there was an inverse relationship with development time and incubation temperature level. Insects develop faster which may oviposit early and hence the population was likely to grow earlier than expected.

Evaluating the significance of paleophylogeographic species distribution models in reconstructing quaternary range-shifts of nearctic chelonians.

The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5–10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic bottlenecks; and (iii) predict threats due to anthropogenic climate change in the future.

Investigating the early Earth faint young Sun problem with a general circulation model

The faint young Sun problem, i.e. the contradiction of a reduced solar luminosity by 15–25% during the Archaean and the geological evidence for relatively high surface temperatures that allowed the presence of liquid water, is still mostly open. It is suggested that the cooling induced by a fainter Sun was e.g. offset by higher levels of greenhouse gases (GHGs) during the Archaean, but achieving the amounts of carbon dioxide (CO2) that are necessary to solve the problem can not be supported by proxy data and the estimates of other additional GHGs diverge.In our study we investigate this problem by using the climate model EMAC with a spectrally resolved irradiance dataset valid for the Archaean epoch of the Earth. Our experimental setup contains a series of model runs which allow the investigation of the role of the continents, the ozone and oxygen content of the atmosphere, the solar luminosity, and the CO2 concentration on the climate of the Archaean.Replacing the present day continents with a global ocean lead to a warming at the surface by ~3K and an intensified hydrological cycle. The generation of planetary waves and their propagation to the middle atmosphere is reduced, which intensifies the polar night jet and decelerates the Brewer–Dobson circulation. Slightly lower global annual mean temperatures can be found for an anoxic atmosphere. The absent ozone heating in the middle atmosphere leads to very low temperatures in the middle atmosphere and a vanishing polar night jet, whereas the subtropical jets and the Hadley circulation are intensified. The reduction of the solar luminosity to 82% of the present value leads to a globally ice-covered planet and very dry conditions. Prescribing 10 times the present atmospheric level of CO2 with the same solar luminosity leads to a broad belt of liquid surface water throughout the year, although the global annual mean temperature is below the freezing point of water. On reducing the solar luminosity to 77% of the present value with the same amount of CO2, the area of ice-free ocean water narrows, but still suggesting a habitable environment during the Archaean for a CO2 concentration consistent with paleosol data.

Recent global-warming hiatus tied to equatorial Pacific surface cooling

Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

Simulation of the influence of historical land cover changes on the global climate

Abstract. In order to estimate biogeophysical effects of historical land cover change on climate during last three centuries, a set of experiments with a climate system model of intermediate complexity (MPM-2) is performed. In response to historical deforestation, the model simulates a decrease in annual mean global temperature in the range of 0.07–0.14 °C based on different grassland albedos. The effect of land cover changes is most pronounced in the middle northern latitudes with maximum cooling reaching approximately 0.6 °C during northern summer. The cooling reaches 0.57 °C during northern spring owing to the large effects of land surface albedo. These results suggest that land cover forcing is important for study on historical climate change and that more research is necessary in the assessment of land management options for climate change mitigation.

Evidence for two abrupt warming events of SST in the last century

We have recently suggested that the warming in the sea surface temperature (SST) since 1900, did not occur smoothly and slowly, but with two rapid shifts in 1925/1926 and 1987/1988, which are more obvious over the tropics and the northern midlatitudes. Apart from these shifts, most of the remaining SST variability can be explained by the El Niño Southern Oscillation and the Pacific Decadal Oscillation (PDO). Here, we provide evidence that the timing of these two SST shifts (around 60 years) corresponds well to the quasi-periodicity of many natural cycles, like that of the PDO, the global and Northern Hemisphere annual mean temperature, the Atlantic Multi-decadal Oscillation, the Inter-Tropical Convergence Zone, the Southwest US Drought data, the length of day, the air surface temperature, the Atlantic meridional overturning circulation and the change in the location of the centre of mass of the solar system. In addition, we show that there exists a strong seasonal link between SST and ENSO over the tropics and the NH midlatitudes, which becomes stronger in autumn of the Northern Hemisphere. Finally, we found that before and after each SST shift, the intrinsic properties of the SST time series obey stochastic dynamics, which is unaffected by the modulation of these two shifts. In particular, the SST fluctuations for the time period between the two SST shifts exhibit 1/f-type long-range correlations, which are frequently encountered in a large variety of natural systems. Our results have potential implications for future climate shifts and crossing tipping points due to an interaction of intrinsic climate cycles and anthropogenic greenhouse gas emissions.

Simulating the mid-Pliocene Warm Period with the CCSM4 model

Abstract. This paper describes the experimental design and model results from a 500 yr fully coupled Community Climate System, version 4, simulation of the mid-Pliocene Warm Period (mPWP) (ca. 3.3–3.0 Ma). We simulate the mPWP using the "alternate" protocol prescribed by the Pliocene Model Intercomparison Project (PlioMIP) for the AOGCM simulation (Experiment 2). Results from the CCSM4 mPWP simulation show a 1.9 °C increase in global mean annual temperature compared to the 1850 preindustrial control, with a polar amplification of ~3 times the global warming. Global precipitation increases slightly by 0.09 mm day−1 and the monsoon rainfall is enhanced, particularly in the Northern Hemisphere (NH). Areal sea ice extent decreases in both hemispheres but persists through the summers. The model simulates a relaxation of the zonal sea surface temperature (SST) gradient in the tropical Pacific, with the El Niño–Southern Oscillation (Niño3.4) ~20% weaker than the preindustrial and exhibiting extended periods of quiescence of up to 150 yr. The maximum Atlantic meridional overturning circulation and northward Atlantic oceanic heat transport are indistinguishable from the control. As compared to PRISM3, CCSM4 overestimates Southern Hemisphere (SH) sea surface temperatures, but underestimates NH warming, particularly in the North Atlantic, suggesting that an increase in northward ocean heat transport would bring CCSM4 SSTs into better alignment with proxy data.

Assessment of climate change adaptation costs for the U.S. road network

The U.S. road network is one of the nation's most important capital assets and is vital to the functioning of the U.S. economy. Maintaining this asset involves approximately $134 billion of government funds annually from Federal, State, and local agencies. Climate change may represent a risk or an opportunity to this network, as changes in climate stress will affect the resources necessary for both road maintenance and construction projects. This paper develops an approach for estimating climate-related changes in road maintenance and construction costs such that the current level of service provided by roads is maintained over time. We estimate these costs under a baseline scenario in which annual mean global temperature increases by 1.5°C in 2050 relative to the historical average and a mitigation scenario under which this increase in mean temperature is limited to 1.0°C. Depending on the nature of the changes in climate that occur in a given area, our analysis suggests that climate change may lead to a reduction in road maintenance and/or construction costs or an increase in costs. Overall, however, our analysis shows that climate change, if unchecked, will increase the annual costs of keeping paved and unpaved roads in service by $785 million in present value terms by 2050. When not discounted, this figure increases to $2.8 billion. Policies to reduce greenhouse gas emissions are estimated to reduce these costs by approximately $280 million in present value terms and by $885 million when not discounted. These costs vary substantially by region and time period, information that should be important for transportation planners at the national, state, and local levels.

Climate responses to historical land cover changes

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 56:147-155 (2013) - DOI: https://doi.org/10.3354/cr01150 Climate responses to historical land cover changes Ye Wang1,2,*, Xiaodong Yan2,3 1College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China 2Key Laboratory of Regional Climate-Environment for East Asia, Chinese Academy of Sciences, Beijing 10029, PR China 3State Key Laboratory of Earth Surface Processes and Resource Ecology (ESPRE), College of Global Change and Earth System Science, Beijing Normal University, 19 Xinjiekouwai Street, Haidian District, Beijing 100875, PR China *Email: wytea@126.com ABSTRACT: This study assessed the biogeophysical effects of land cover change on climate using MPM-2 during the past millennium. Simulations based on the Climate and Environmental Retrieval and Archive (CERA) land cover dataset were carried out to equilibrium from AD 800 to 2000 after a spin-up time of 5300 yr. We concluded that there was a cooling biogeophysical effect of about 0.13°C in global mean annual temperature in response to historical deforestation, with a maximum cooling of 0.5°C over Eurasia and a minimum cooling of 0.02°C at low latitudes over the Southern Hemisphere. Much larger contrasts were found on a seasonal scale, while these changes were largely offset on an annual scale. Seasonally, cooling occurred in the middle northern latitudes and warming occurred in the low southern latitudes due to historical deforestation. The effect of land cover change was most pronounced over Eurasia, with a maximum cooling of approximately 0.8°C at middle latitudes during summer and a maximum warming of 0.1°C at low latitudes over the Southern Hemisphere during the Northern Hemisphere summer, owing to the changes in albedo and precipitation. These results suggest that changes in land cover triggered a chain of feedbacks in the climate system, and they highlight the need for further research in this area. KEY WORDS: Biogeophysical effects · Climate change · Land cover change · Earth system model at intermediate complexity · EMIC · Modeling Full text in pdf format PreviousNextCite this article as: Wang Y, Yan X (2013) Climate responses to historical land cover changes. Clim Res 56:147-155. https://doi.org/10.3354/cr01150 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 56, No. 2. Online publication date: March 26, 2013 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2013 Inter-Research.