Changes In Mean Annual Temperature Research Articles

The effects of 1.5 and 2 degrees of global warming on Africa in the CORDEX ensemble

There is a general lack of information about the potential effects of 1.5, 2 or more degrees of global warming on the regional climates within Africa, and most studies that address this use data from coarse resolution global models. Using a large ensemble of CORDEX Africa simulations, we present a pan-African overview of the effects of 1.5 and 2 °C global warming levels (GWLs) on the African climate. The CORDEX simulations, consistent with their driving global models, show a robust regional warming exceeding the mean global one over most of Africa. The highest increase in annual mean temperature is found over the subtropics and the smallest one over many coastal regions. Projected changes in annual mean precipitation have a tendency to wetter conditions in some parts of Africa (e.g. central/eastern Sahel and eastern Africa) at both GWLs, but models’ agreement on the sign of change is low. In contrast to mean precipitation, there is a consistent increase in daily precipitation intensity of wet days over a large fraction of tropical Africa emerging already at 1.5 °C GWL and strengthening at 2 °C. A consistent difference between 2 °C and 1.5 °C warmings is also found for projected changes in annual mean temperature and daily precipitation intensity. Our study indicates that a 0.5 °C further warming (from 1.5 °C–2 °C) can indeed produce a robust change in some aspects of the African climate and its extremes.

Global patterns of dead fine root stocks in forest ecosystems

AbstractAimDead fine roots are crucial components of the carbon cycle in global forest ecosystems. Despite their importance, knowledge concerning geographical patterns of dead fine root pools (necromass) and factors influencing their dynamics remain scarce across the globe.LocationGlobal.MethodsWe analysed 136 published case studies covering 169 forest sites located throughout the world to identify broad patterns of necromass and biomass (living fine root pools) and to determine the responses to climate, edaphic gradients and stand properties.ResultsW‐shaped pattern of forest necromass with latitude, from the Southern Hemisphere via the equator to the Northern Hemisphere, was observed. Specifically, more necromass was found at both low (tropical forests) and high latitudes (boreal forests), whereas less necromass was found at mid latitudes (temperate forests), which is in line with patterns of carbon stocks in soils at the global scale. Broad‐leaf forests had greater necromass than needle‐leaf forests, and fine root necromass of the two forest types showed opposing trends in response to shifts in mean annual precipitation and different sensitivities to changes in mean annual temperature and edaphic properties (e.g. soil carbon/nitrogen ratio and pH). Necromass increased with soil organic layer thickness and stand age for both forest types.Main conclusionsThe hemispheric symmetrical necromass distribution is likely determined by changes in environmental conditions across latitudes. Different responses of dead fine roots in broad‐leaf and needle‐leaf forests may be caused by their distinct allocation and accumulation of carbon in relation to climate and to edaphic and forest characteristics at the global scale. Our results have important implications for accurate quantification and modelling of forest ecosystem carbon stocks and cycles and for assessments of their sensitivity and stability in a changing climate.

Model evidence for a seasonal bias in Antarctic ice cores

Much of the global annual mean temperature change over Quaternary glacial cycles can be attributed to slow ice sheet and greenhouse gas feedbacks, but analysis of the short-term response to orbital forcings has the potential to reveal key relationships in the climate system. In particular, obliquity and precession both produce highly seasonal temperature responses at high latitudes. Here, idealized single-forcing model experiments are used to quantify Earth’s response to obliquity, precession, CO2, and ice sheets, and a linear reconstruction methodology is used to compare these responses to long proxy records around the globe. This comparison reveals mismatches between the annual mean response to obliquity and precession in models versus the signals within Antarctic ice cores. Weighting the model-based reconstruction toward austral winter or spring reduces these discrepancies, providing evidence for a seasonal bias in ice cores.

Trend analysis of temperature and rainfall in south gonder zone, anhara ethiopia

This study mainly focuses on exploring trend analysis of temperature and rainfall in the case of south Gonder zone. The analysis is based on the temperature and rainfall variation in south Gonder zone over three stations at Addis Zemen, Nefas Mewcha and Mekane Eyesus. The duration of the study period for temperature and rainfall data was chosen as 1996-2015 for Addis Zemen, 1986-2015 for Nefas Mewcha and 1996-2015 for Mekane Eyesus. The Belg rainfall have been found much more variable (>30%) than the Kiremet rainfall in which the coefficient of variation is greater than 30% over the study area. The findings of the non-parametric Mann-Kendall test revealed that there was no significant trend in the annual and seasonal rainfall data whereas monthly rainfall of April and November shown statistically significant increasing trendover the study area. However, the trend was not significant, the annual, the Kiremet and monthly rainfall during June, August and November shows an increasing particularly November was also statically significant as the computed p-value is less than the significance level α = 0.05.On the other hand, the Belg rainfall and monthly rainfall of March and April shows a decreasing trend. Statistically significant increases of mean annual temperature have been found in Addis Zemen and Nefas Mocha whereas statistically insignificant decrease of mean annual temperature has found in Mekane Eyesus. On the other hand, statistically significant increase of annual maximum temperature has been found in Addis Zemen while statistically insignificant increase of annual maximum temperature have been found for Nefas Mewcha and Mekane Eyesus station. Besides, statistically significant increase of annual minimum temperature has been found in Nefas Mewcha whereas statistically insignificant increase of annual minimum temperature has been found in Addis Zemen and Mekane Eyesus. The rates of change in mean annual temperature for Addis Zemen 1.698 0 c per 20 years and Nefas Mocha 0.813 0 c per 30 years have been found greater than the rate of change which was found at national and global level. Therefore, it is recommended that small scale study should be undertaken to clearly detect the rate of climate change and to develop appropriate adaptation strategies for the given agricultural system with the prevailing climatic conditions.

Variation trend and response relationship of temperature, precipitation and runoff in Baiyangdian Lake Basin

As the largest freshwater lake in the North China Plain, Baiyangdian Lake is a key hydro-confluence that is critical for flood prevention, sedimentation mitigation, irrigation, water supply and maintenance of ecological balance of the area. Since the 1960s, surface runoff in Baiyangdian Basin has continuously dropped, water quantity greatly reduced and lake-drying frequency increased due to the impact of climate change and human activities. The decreasing water quantity has reduced ecological function of the lake, further affecting socio-economic development and ecological security in the region. Using observed daily temperature and precipitation data at 7 meteorological stations along with monthly runoff data from 3 typical hydrological stations for the period 1957-2012, the change characteristics in temperature, precipitation and runoff in the Baiyangdian Lake Basin were analyzed. In this study, the cumulative anomaly method, Mann-Kendall test and Morlet wavelet analysis method were used to determine the trends and abrupt changes in mean annual temperature, precipitation and runoff. The purpose of this study was to develop data support and reference base for improving ecological environment and reasonable utilization of water resources in the area. The results showed that the climate in the study area had a significant warming trend with an abrupt increase of temperature since 1988. Especially, the increase of temperature in both winter and summer contributed more to temperatures rising. Annual precipitation showed a decreasing trend with obvious fluctuation. The decrease in summer precipitation (1.72 mm·a-1) was higher than that in the other seasons. Increasing temperature along with decreasing precipitation were the dominant trends, further aggravating dry and hot climatic conditions and lake-drying in the region. There was an obvious decreasing trend in runoff due to the effect of temperature and precipitation. There was a negative correlation between runoff and temperature and a positive correlation between runoff and precipitation at annual scale. At seasonal scale, runoff was positively correlated with temperature and precipitation. Summer runoff in Fuping, Daomaguan and Zijingguan hydrological stations decreased by 0.85 m3·s-1·a-1, 0.72 m3·s-1·a-1 and 0.66 m3·s-1·a-1, respectively. The intervals of change in mean annual temperature, precipitation and runoff were obvious. Also the fluctuations in runoff and precipitation were consistent, suggesting that the response of runoff to precipitation was more prominent. The change in runoff was not only influenced by temperature and precipitation, but also by other climatic factors, water conservancy projects, agriculture and local geological conditions. In future studies, it was needed to further analyze the effect of each factor on the runoff in order to comprehensively understand the driving factors of runoff in the basin.

Metabolic heat production by human and animal populations in cities.

Anthropogenic heating from building energy use, vehicle fuel consumption, and human metabolism is a key term in the urban energy budget equation. Heating from human metabolism, however, is often excluded from urban energy budgets because it is widely observed to be negligible. Few reports for low-latitude cities are available to support this observation, and no reports exist on the contribution of domestic animals to urban heat budgets. To provide a more comprehensive view of metabolic heating in cities, we quantified all terms of the anthropogenic heat budget at metropolitan scale for the world's 26 largest cities, using a top-down statistical approach. Results show that metabolic heat release from human populations in mid-latitude cities (e.g. London, Tokyo, New York) accounts for 4-8% of annual anthropogenic heating, compared to 10-45% in high-density tropical cities (e.g. Cairo, Dhaka, Kolkata). Heat release from animal populations amounts to <1% of anthropogenic heating in all cities. Heat flux density from human and animal metabolism combined is highest in Mumbai-the world's most densely populated megacity-at 6.5Wm-2, surpassing heat production by electricity use in buildings (5.8Wm-2) and fuel combustion in vehicles (3.9Wm-2). These findings, along with recent output from global climate models, suggest that in the world's largest and most crowded cities, heat emissions from human metabolism alone can force measurable change in mean annual temperature at regional scale.

An energy balance perspective on regional CO2-induced temperature changes in CMIP5 models

An energy balance decomposition of temperature changes is conducted for idealized transient CO2-only simulations in the fifth phase of the Coupled Model Intercomparison Project. The multimodel global mean warming is dominated by enhanced clear-sky greenhouse effect due to increased CO2 and water vapour, but other components of the energy balance substantially modify the geographical and seasonal patterns of the change. Changes in the net surface energy flux are important over the oceans, being especially crucial for the muted warming over the northern North Atlantic and for the seasonal cycle of warming over the Arctic Ocean. Changes in atmospheric energy flux convergence tend to smooth the gradients of temperature change and reduce its land-sea contrast, but they also amplify the seasonal cycle of warming in northern North America and Eurasia. The three most important terms for intermodel differences in warming are the changes in the clear-sky greenhouse effect, clouds, and the net surface energy flux, making the largest contribution to the standard deviation of annual mean temperature change in 34, 29 and 20 % of the world, respectively. Changes in atmospheric energy flux convergence mostly damp intermodel variations of temperature change especially over the oceans. However, the opposite is true for example in Greenland and Antarctica, where the warming appears to be substantially controlled by heat transport from the surrounding sea areas.

Climate change may threaten habitat suitability of threatened plant species within Chinese nature reserves.

Climate change has the potential to alter the distributions of threatened plant species, and may therefore diminish the capacity of nature reserves to protect threatened plant species. Chinese nature reserves contain a rich diversity of plant species that are at risk of becoming more threatened by climate change. Hence, it is urgent to identify the extent to which future climate change may compromise the suitability of threatened plant species habitats within Chinese nature reserves. Here, we modelled the climate suitability of 82 threatened plant species within 168 nature reserves across climate change scenarios. We used Maxent modelling based on species occurrence localities and evaluated climate change impacts using the magnitude of change in climate suitability and the degree of overlap between current and future climatically suitable habitats. There was a significant relationship between overlap with current and future climate suitability of all threatened plant species habitats and the magnitude of changes in climate suitability. Our projections estimate that the climate suitability of more than 60 threatened plant species will decrease and that climate change threatens the habitat suitability of plant species in more than 130 nature reserves under the low, medium, and high greenhouse gas concentration scenarios by both 2050s and 2080s. Furthermore, future climate change may substantially threaten tree plant species through changes in annual mean temperature. These results indicate that climate change may threaten plant species that occur within Chinese nature reserves. Therefore, we suggest that climate change projections should be integrated into the conservation and management of threatened plant species within nature reserves.

Organic matter losses in German Alps forest soils since the 1970s most likely caused by warming

Climate warming is expected to induce soil organic carbon losses in mountain soils that result, in turn, in reduced soil fertility, reduced water storage capacity and positive feedback on climate change. Here we combine two independent sets of measurements of soil organic carbon from forest soils in the German Alps—repeated measurements from 1976 to 2010 and from 1987 to 2011—to show that warming has caused a 14% decline in topsoil organic carbon stocks. The decreases in soil carbon occurred over a period of significant increases in six-month summer temperatures, with the most substantial decreases occurring at sites with large changes in mean annual temperature. Organic carbon stock decreases were largest—on average 32%—in forest soils with initial topsoil organic carbon stocks greater than 8 kg C m−2, which can be found predominantly on calcareous bedrock. However, organic carbon stocks of forest soils with lower initial carbon stocks, as well as soils under pasture or at elevations above 1,150 m, have not changed significantly. We conclude that warming is the most likely reason for the observed losses of soil organic carbon, but that site, land use and elevation may ameliorate the effects of climate change. Soil carbon concentrations are sensitive to climate warming. Pairs of measurements of forest soil carbon stocks in the German Alps reveal that topsoil carbon concentrations declined as air temperatures rose between 1976 and 2011.

Late-Holocene and Little Ice Age palaeoenvironmental change inferred from pollen analysis, Isla de los Estados, Argentina

We present pollen and spore analysis from a peat-bog section from southwestern Isla de los Estados (Staaten Island), Tierra del Fuego to better understand late-Holocene environmental change in southernmost Patagonia. The island's position as the easternmost landmass at the southernmost of South America, places it squarely within the influence of the southern westerly winds (SWW) and the Antarctic Circumpolar Current, and so makes the island a unique location to document the palaeoecological response to climate change during the late Quaternary. We compare our Nothofagus pollen record from Bahía Franklin with other Nothofagus pollen records from Isla de los Estados and Tierra del Fuego. Nothofagus has been shown to respond to changes in mean annual temperature in the southern latitudes under cooler climate with little seasonality in precipitation. We also evaluate the correspondence between these changes in vegetation to other late-Holocene environmental proxies that include variations in sea surface temperature (SST) from the Beagle Channel and records of past glacier fluctuations. Our results show that low concentrations of Nothofagus pollen existed at Bahía Franklin at about 4000 cal yr BP. Climate ameliorated between ca. 3500 and 500 cal yr BP based on an increase in frequency and concentration values of Nothofagus and Drimys winteri. Between about 500 and 50 cal yr BP, the pollen record revealed a noticeable decline in the forest density. We interpret the decline in forest density in Isla de los Estados between 500 and ∼50 yr cal BP as a response to cold and windy conditions during the Little Ice Age (LIA). Our interpretation from our Nothofagus pollen record broadly agrees with regional cooling recorded in reconstructed SST of the Beagle Channel and with glacier expansion in the Fuegian Cordillera.

High plant endemism in China is partially linked to reduced glacial‐interglacial climate change

AbstractAimEndemic species are hypothesized to particularly occur in areas with relatively stable climates during the Quaternary glacial‐interglacial oscillations (orbitally forced species' range dynamics hypothesis). This hypothesis has received support in global studies and studies from regions highly affected by glaciations. Here, we test its applicability to Chinese endemic species, thereby testing it in a region that was relatively mildly affected by glaciations.LocationChina.MethodsWe tested for associations between endemic species richness and Quaternary climate change, current climate and topography. Changes in mean annual temperature (MAT) and annual precipitation (MAP) between the Last Glacial Maximum and present were used to describe Quaternary climate change. We used simultaneous autoregressive (SAR) models to account for spatial autocorrelation in predictors, and Random Forest modelling to deal with non‐linear relationships and better handle multicollinearity among predictor variables. To get a deeper understanding of the mechanisms involved we also performed analyses based on growth‐form (woody versus herbaceous plants) and species age (palaeo‐ and neoendemics).ResultsSingle‐predictor SAR models showed that glacial‐interglacial MAT velocity always has higher explanatory power than current climate (with a pseudo r2 difference of 0.581–0.604 between the best palaeoclimate and current climate predictors for models for all endemic plants). Model selection on multivariate SAR models (based on Akaike weights) and Random Forest modelling (based on correlations between predicted and observed species richness) always included at least one variable representing Quaternary climate change as well as one or more current climate variables. Quaternary climate‐change variables were generally of similar strength to the current climate predictors. Notably, the summed Akaike weight across all models in the relevant model set was always 1 for glacial‐interglacial MAT velocity. There were no clear differences with respect to growth forms or species age in the estimated importance of Quaternary climate change.Main conclusionsThe consistent association between long‐term climatic stability and high plant endemism in China provides strong evidence for the importance of Quaternary glacial‐interglacial climate changes in shaping the distribution of endemic species, even in regions relatively mildly affected by glaciations. Hence, even moderate climate changes may have strong, long‐term effects on species diversity patterns.

Assessment of temporal and spatial changes of future climate in the Jhelum river basin, Pakistan and India

Abstract The present study investigated future temporal and spatial changes in maximum temperature, minimum temperature, and precipitation in two sub-basins of the Jhelum River basin—the Two Peak Precipitation basin (TPPB) and the One Peak Precipitation basin (OPPB)—and in the Jhelum River basin on the whole, using the statistical downscaling model, SDSM. The Jhelum River is one of the biggest tributaries of the Indus River basin and the main source of water for Mangla reservoir, the second biggest reservoir in Pakistan. An advanced interpolation method, kriging, was used to explore the spatial variations in the study area. Validation results showed a better relationship between simulated and observed monthly time series as well as between seasonal time series relative to daily time series, with an average R2 of 0.92–0.97 for temperature and 0.22–0.62 for precipitation. Mean annual temperature was projected to rise significantly in the entire basin under two emission scenarios of HadCM3 (A2 and B2). However, these changes in mean annual temperature were predicted to be higher in the TPPB than the OPPB. On the other hand, mean annual precipitation showed a distinct increase in the TPPB and a decrease in the OPPB under both scenarios. In the case of seasonal changes, spring in the TPPB and autumn in the OPPB were projected to be the most affected seasons, with an average increase in temperature of 0.43–1.7 °C in both seasons relative to baseline period. Summer in the TPPB and autumn in the OPPB were projected to receive more precipitation, with an average increase of 4–9% in both seasons, and winter in the TPPB and spring in the OPPB were predicted to receive 2–11% less rainfall under both future scenarios, relative to the baseline period. In the case of spatial changes, some patches of the basin showed a decrease in temperature but most areas of the basin showed an increase. During the 2020s (2011–2040), about half of the basin showed a decrease in precipitation. However, in the 2080s (2071–2099), most parts of the basin were projected to have decreased precipitation under both scenarios.

Water footprint assessment considering climate change effects on future agricultural production in Mediterranean region

Climate change significantly affects every day’s human activities such as agriculture and tourism by altering the composition and parameters of global atmosphere over long period of time. In Greece, a substantial part of the national gross domestic product comes from agricultural production the efficiency (e.g. crop yield) of which mainly depends on adequacy and sufficiency of resources such as water and soil fertility. In this concept, the water footprint (WF) could be used as a monitoring indicator to evaluate applied agricultural schemes and potential adaptation measures in cultivated regions in Greece with respect to consumption of freshwater resources and deterioration of water receptors considering climate change scenarios. In the present paper, agricultural WF in two plains in Crete, Messara and Chania, are calculated in order to estimate the environmental impacts of the currently applied agricultural schemes on freshwater resources and soil productivity in the two plains. The analysis was based on a climate change scenario that has been developed up to 2100 to assess the effects of precipitation and temperature variability on crop yield and consumption of freshwater resources in the two plains. The results analysis showed that for all the crops in both Messara and Chania plains the two components of WF, blue and green have a substantial contribution to the overall WF of crops. However, the changes in mean annual temperature and precipitation as they are estimated in the examined climate change scenario may affect the evolution of blue and green WF till 2100 by alternating the source of consumed water between water reserves and rainfall. In both also Cretan plains is observed that an estimation of future water needs based on WF indicator could be obtained considering the particular climate scenario only for irrigated crops due to the similar trend that is followed by temperature and total WF. A similar estimation could not be made for rain-fed crops due to the high variability in future precipitation values (low R2). Finally, the impact of climate change with respect to WF estimation is considerably higher in water scarce areas like Messara plain. The crop yield sensitivity analysis for citrus demonstrated that there is no pattern by which it is possible to estimate their crop yield considering only mean monthly temperature and precipitation values. The crop yield is decisively influenced by the timing that the different rainfall and temperature events happened during the growing season. By concluding special concern should be paid on adaptation measures in local, regional, and national level in order to control the impact of climate change on crop yields.

Detection and attribution analysis of annual mean temperature changes in China

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 63:61-71 (2015) - DOI: https://doi.org/10.3354/cr01283 Detection and attribution analysis of annual mean temperature changes in China Ying Xu1,*, Xuejie Gao2, Ying Shi1, Zhou Botao1 1National Climate Center, China Meteorological Administration, 100081 Beijing, China 2Climate Change Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029 Beijing, China *Corresponding author: xuying@cma.gov.cn ABSTRACT: Using an optimal fingerprinting method and the Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model simulations, we attempted to quantify the human contribution to the observed annual mean temperature change that occurred over China between 1961 and 2005. Results indicate that the combined effects of greenhouse gases and sulfate aerosol forcing are clearly detectable in the observed annual mean temperature change. Effects of anthropogenic and natural forcings are separately detectable, and the climate response to greenhouse gas forcing can be identified clearly and robustly. Our results also show that only when anthropogenic forcing is involved can the observed changes in China’s mean temperature from 1961 to 2005 be explained. KEY WORDS: Detection and attribution · Climate change · CMIP5 · Models Full text in pdf format PreviousNextCite this article as: Xu Y, Gao X, Shi Y, Botao Z (2015) Detection and attribution analysis of annual mean temperature changes in China. Clim Res 63:61-71. https://doi.org/10.3354/cr01283 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 63, No. 1. Online publication date: April 01, 2015 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2015 Inter-Research.

Changes and trends in maximum, minimum and mean temperature series in Iran

AbstractThe variations of Iran temperature is studied during 1961–2010. Mann–Kendall tests show a general dominating positive temperature trend over most parts of Iran with the rate of change varying from 0.09 to 0.38 °C decade−1. Also, the minimum temperature increase (0.34 °C decade−1) is greater than maximum temperature (0.15 °C decade−1). A more definite trend of warming occurs in summer and spring than winter and autumn. Moreover, the results show that the warm climate regions in Iran are warming at a higher rate than cold climate regions. Pettitt's test also suggesting the abrupt upward change in mean annual temperature, occurs in the late 1990s.

Change of lake area in the southeastern part of China’s Badain Jaran Sand Sea and its implications for recharge sources

Understanding the relationship between the changes in lake water volume and climate change can provide valuable information to the recharge sources of lake water. This is particularly true in arid areas such as the Badain Jaran Sand Sea, an ecologically sensitive area, where the recharge sources of lakes are heatedly debated. In this study, we determined the areas of 50 lakes (representing 70% of the total permanent lakes in this sand sea) in 1967, 1975, 1990, 2000 and 2010 by analyzing remote-sensing images using image processing and ArGIS software. In general, the total lake area decreased from 1967 to 1990, remained almost unchanged from 1990 to 2000, and increased from 2000 to 2010. Analysis of the relationship between these changes and the contemporaneous changes in annual mean temperature and annual precipitation in the surrounding areas suggests that temperature has significantly affected the lake area, but that the influence of precipitation was minor. These results tend to support the palaeo-water recharge hypothesis for lakes of the Badain Jaran Sand Sea, considering the fact that the distribution and area of lakes are closely related to precipitation and the size of mega-dunes, but the contemporaneous precipitation can hardly balance the lake water.

Temperature effects on long‐term population dynamics in a parasitoid–host system

Long‐term environmental changes will likely alter the strengths of interactions between species and consequently their population dynamics, leading to changes in the stability of ecological systems. While an increasing number of empirical studies have shown that environmental changes can alter the strengths of species interactions, these studies are typically short (&lt;1–2 generations) and therefore give only partial information about longer term population dynamics. To focus on longer term dynamics, we investigated population cycles of pea aphids and their most common parasitoid, Aphidius ervi, in Wisconsin, USA. Data collected over three years in alfalfa fields showed an apparent host–parasitoid population cycle. Furthermore, higher pea aphid population growth rates and increased parasitism were correlated with higher naturally occurring temperatures. While these effects were observed with seasonal fluctuations in temperature, they beg the question of how long‐term changes in mean annual temperature might change aphid–parasitoid population cycles, a question which we further pursued with laboratory experiments. To quantify temperature‐dependent demographic parameters, we used short‐term (&lt;1 generation) experiments conducted at 20°C and 27°C. The higher temperature increased aphid and parasitoid development rates, adult aphid life span and fecundity, and parasitoid attack rates. We then conducted multi‐generation population‐level laboratory experiments to reveal the effects of temperature (20°C vs. 27°C) on population dynamics. We fit the resulting time series data using a nonlinear age‐structured state‐space model to estimate population‐level processes that could not be estimated in short‐term laboratory experiments. Using the model, we parsed out the demographic rates that had the largest impacts on aphid–parasitoid population cycles. This analysis showed that there were frequent contrasts in the effects of temperature operating through different demographic rates. For example, the temperature‐dependent increase in aphid development rate decreased cycle amplitude, while the increase in parasitoid attack rate increased cycle amplitude. There were also striking interactions among demographic rates. For example, the temperature‐dependent increase in aphid development rate could either increase or decrease the cycle period depending on the values of other demographic rates. Although these complexities make predictions difficult, overall they suggest that increasing long‐term mean temperature will decrease the period, increase the amplitude, and tend to destabilize pea aphid–A. ervi dynamics.

The impact of astronomical forcing on the Late Devonian greenhouse climate

The geological record of the Paleozoic often exhibits cyclic features, in many cases the result of changes in paleoclimate. However, a thorough understanding of the processes that were driving Paleozoic climate change has not yet been reached. The main reason is relatively poor time-control on Paleozoic paleoclimate proxy records. This problem can be overcome by the identification of cyclic features resulting from astronomical climate forcing in the stratigraphic record. To correctly identify these cyclic features, it is necessary to quantify the effects of astronomical climate forcing under conditions different from today. In this work, we apply Late Devonian (375Ma) boundary conditions to the Hadley Centre general circulation model (HadSM3). We estimate the response of Late Devonian climate to astronomical forcing by keeping all other forcing factors (e.g. paleogeography, pCO2, vegetation distribution) fixed. Thirty-one different “snapshots” of Late Devonian climate are simulated, by running the model with different combinations of eccentricity (e), obliquity (ε) and precession (ω˜). From the comparison of these 31 simulations, it appears that feedback mechanisms play an important role in the conversion of astronomically driven insolation variations into climate change, such as the formation of sea-ice and the development of an extensive snow cover on Gondwana. We compare the “median orbit” simulation to lithic indicators of paleoclimate to evaluate whether or not HadSM3 validly simulates Late Devonian climates. This comparison suggests that the model correctly locates the major climate zones. This study also tests the proposed link between the formation of ocean anoxia and high eccentricity (De Vleeschouwer et al., 2013) by comparing the δ18Ocarb record of the Frasnian–Famennian boundary interval from the Kowala section (Poland) with a simulated time series of astronomically forced changes in mean annual temperature at the paleolocation of Poland. The amplitude of climate change suggested by the isotope record is greater than that of the simulated climate. Hence, astronomically forced climate change may have been further amplified by other feedback mechanisms not considered here (e.g. CO2 and vegetation). Finally, the geologic and simulated time series correlate best when the Frasnian–Famennian negative isotope excursion aligns with maximum mean annual temperature in Poland, which is obtained when eccentricity and obliquity are simultaneously high. This finding supports a connection between Devonian ocean anoxic events and astronomical climate forcing.

A framework for modeling uncertainty in regional climate change

In this study, we present a new modeling framework and a large ensemble of climate projections to investigate the uncertainty in regional climate change over the United States (US) associated with four dimensions of uncertainty. The sources of uncertainty considered in this framework are the emissions projections, global climate system parameters, natural variability and model structural uncertainty. The modeling framework revolves around the Massachusetts Institute of Technology (MIT) Integrated Global System Model (IGSM), an integrated assessment model with an Earth System Model of Intermediate Complexity (EMIC) (with a two-dimensional zonal-mean atmosphere). Regional climate change over the US is obtained through a two-pronged approach. First, we use the IGSM-CAM framework, which links the IGSM to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). Second, we use a pattern-scaling method that extends the IGSM zonal mean based on climate change patterns from various climate models. Results show that the range of annual mean temperature changes are mainly driven by policy choices and the range of climate sensitivity considered. Meanwhile, the four sources of uncertainty contribute more equally to end-of-century precipitation changes, with natural variability dominating until 2050. For the set of scenarios used in this study, the choice of policy is the largest driver of uncertainty, defined as the range of warming and changes in precipitation, in future projections of climate change over the US.

Assessing divergent SST behavior during the last 21 ka derived from alkenones andG. ruber-Mg/Ca in the equatorial Pacific

Equatorial Pacific SST reconstructions derived from Mg/Ca ratios in planktonic foraminifera Globigerinoides ruber and from alkenone-producing coccolithophorids record different trends throughout the Holocene and the last deglaciation. We set forth the hypothesis that their diverging behavior may be related to different seasonal sensitivities which result from the annually varying production rates of alkenone-producing coccolithophorids and of G. ruber. Using a series of transient paleoclimate model simulations forced with the time-varying forcing history over the last 21 ka, a good qualitative agreement is found between simulated boreal winter temperatures and alkenone-SST reconstructions as well as between simulated boreal summer temperatures and reconstructed Mg/Ca-based SST variations. Pronounced features in the reconstructions that can be readily explained by the conjectured seasonal biases include the mismatch in middle-to-late Holocene temperature trends and the different onsets of deglacial climate change in the eastern equatorial Pacific. The analysis presented here further suggests that through combinations of Mg/Ca and alkenone SST reconstructions information can be gained on annual mean temperature changes and the amplitude of the seasonal cycle in SST. Our study concludes by discussing potential weaknesses of the proposed model-derived seasonal bias interpretation of tropical Pacific SST proxies in terms of present-day core-top data, sediment trap studies, and satellite-based observations of chlorophyll.