Global Mean Temperature Rise Research Articles

Increasing impacts of climate change upon ecosystems with increasing global mean temperature rise

Increasing impacts of climate change upon ecosystems with increasing global mean temperature rise

Efficient climate policies under technology and climate uncertainty

This article explores efficient climate policies in terms of investment streams into fossil and renewable energy technologies. The investment decisions maximise social welfare while observing a probabilistic guardrail for global mean temperature rise under uncertain technology and climate parameters. Such a guardrail constitutes a chance constraint, and the resulting optimisation problem is an instance of chance constrained programming, not stochastic programming as often employed. Our analysis of a model of economic growth and endogenous technological change, MIND, suggests that stringent mitigation strategies cannot guarantee a very high probability of limiting warming to 2 °C since preindustrial time under current uncertainty about climate sensitivity and climate response time scale. Achieving the 2 °C temperature target with a probability P⁎ of 75% requires drastic carbon dioxide emission cuts. This holds true even though we have assumed an aggressive mitigation policy on other greenhouse gases from, e.g., the agricultural sector. The emission cuts are deeper than estimated from a deterministic calculation with climate sensitivity fixed at the P⁎ quantile of its marginal probability distribution (3.6 °C). We show that earlier and cumulatively larger investments into the renewable sector are triggered by including uncertainty in the technology and climate response time scale parameters. This comes at an additional GWP loss of 0.3%, resulting in a total loss of 0.8% GWP for observing the chance constraint. We obtained those results with a new numerical scheme to implement constrained welfare optimisation under uncertainty as a chance constrained programming problem in standard optimisation software such as GAMS. The scheme is able to incorporate multivariate non-factorial probability measures such as given by the joint distribution of climate sensitivity and response time. We demonstrate the scheme for the case of a four-dimensional parameter space capturing uncertainty about climate and technology.

Regulatory standards and barriers to improved performance for housing

This paper argues that energy efficiency in dwellings probably needs to improve more rapidly, and to higher levels, than is likely to be achieved by current policy if global mean temperature rise is to be held to 2 K. History suggests that achieving real reductions in carbon emissions is not easy in this sector. Future progress will require significant changes in the way policy is formulated and implemented.

New climate change scenarios for the Netherlands

A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future.

Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature

Abstract There is considerable evidence for solar influence on the Earth's pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.

Critical considerations for future action during the second commitment period: A small islands’ perspective

Abstract If the objective of the United Nations Framework Convention on Climate Change (UNFCCC) is to be achieved, Parties must commit themselves to meeting meaningful long‐term targets that, based on current knowledge, would minimize the possibility of irreversible climate change. Current indications are that a global mean temperature rise in excess of 2–3 °C would enhance the risk of destabilizing the climate system as we know it, and possibly lead to catastrophic change such as a shutdown of the deep ocean circulation, and the disintegration of the West Arctic Ice Sheet. Observations have shown that for many small island developing States (SIDS), life‐sustaining ecosystems such as coral reefs, already living near the limit of thermal tolerance, are highly climate‐sensitive, and can suffer severe damage from exposure to sea temperatures as low as 1 °C above the seasonal maximum. Other natural systems (e.g., mangroves) are similarly susceptible to relatively low temperature increases, coupled with small increments of sea level rise. Economic and social sectors, including agriculture and human health, face similar challenges from the likely impacts of projected climate change. In light of known thresholds, this paper presents the view that SIDS should seek support for a temperature cap not exceeding 1.5–2.0 °C above the pre‐industrial mean. It is argued that a less stringent post‐Kyoto target would frustrate achievement of the UNFCCC objective. The view is expressed that all countries which emit significant amounts of greenhouse gases should commit to binding reduction targets in the second commitment period, but that targets for developing countries should be less stringent than those agreed for developed countries. Such an arrangement would be faithful to the principles of equity and would ensure that the right of Parties to attain developed country status would not be abrogated.

The Anthropocene, global change and sleeping giants: where on Earth are we going?

The Anthropocene, global change and sleeping giants: where on Earth are we going?

Uncertainties in climate change scenarios for the Czech Republic

Monthly series from 7 Global Climate Models (GCMs) were used to estimate forthcom- ing changes in global solar radiation, precipitation amount, daily average temperature, and daily temperature range in the Czech region. Scenarios were constructed using the pattern scaling tech- nique: the standardised scenario, which relates the climate variable responses to a 1°C rise in global mean temperature (TG), was multiplied by the predicted change (ΔTG). The standardised scenarios were determined from the GCM runs, ΔTG values were calculated by the simple climate model MAGICC. Two groups of uncertainties were analysed: (1) uncertainties in the standardised scenario, with (1a) inter-GCM variability, (1b) internal GCM variability, (1c) uncertainty due to the choice of the site (within the Czech territory), (1d) uncertainty involved in the regression technique; (2) uncer- tainties in ΔTG, with (2a) choice of the emission scenario, (2b) value of the climate sensitivity factor. In the case of Group 1, (1a) dominated, (1b) was in some cases similar to (1a), and (1c) was nearly neg- ligible; regression uncertainty (1d) indicated that the climate variable changes are often statistically insignificant. In the case of Group 2, uncertainty due to climate sensitivity (2b) dominated for the nearest future, but uncertainty in emission scenarios (2a) attained greater importance later in the 21st century. The mean magnitude of the effect of aerosols on changes in temperature and precipitation was mostly lower than its inter-GCM variability, which was lower than (in the case of the tempera- ture changes) or similar to (in the case of precipitation) the inter-GCM uncertainty in greenhouse gas (GHG) simulations. A stochastic model was developed to assess the combined effect of inter-GCM uncertainty, regression uncertainty, and uncertainty in ΔTG. While the overall uncertainty in the tem- perature scenarios was dominated by inter-GCM uncertainty and ΔTG uncertainty, the aggregated uncertainty in the precipitation scenarios was dominated by inter-GCM uncertainty only.

Origins and estimates of uncertainty in predictions of twenty-first century temperature rise.

Predictions of temperature rise over the twenty-first century are necessarily uncertain, both because the sensitivity of the climate system to changing atmospheric greenhouse-gas concentrations, as well as the rate of ocean heat uptake, is poorly quantified and because future influences on climate-of anthropogenic as well as natural origin-are difficult to predict. Past observations have been used to help constrain the range of uncertainties in future warming rates, but under the assumption of a particular scenario of future emissions. Here we investigate the relative importance of the uncertainty in climate response to a particular emissions scenario versus the uncertainty caused by the differences between future emissions scenarios for our estimates of future change. We present probabilistic forecasts of global-mean temperatures for four representative scenarios for future emissions, obtained with a comprehensive climate model. We find that, in the absence of policies to mitigate climate change, global-mean temperature rise is insensitive to the differences in the emissions scenarios over the next four decades. We also show that in the future, as the signal of climate change emerges further, the predictions will become better constrained.

Responsibility for past and future global warming: Uncertainties in attributing anthropogenic climate change

During the negotiations on the Kyoto Protocol, Brazil proposed a methodology to link the relative contribution of Annex I Parties to emission reductions with the relative contributions of Parties to the global-mean temperature increase. The proposal was not adopted during the negotiations but referred to the Subsidiary Body for Scientific and Technological Advice for consideration of its methodological aspects. In this context we analyze the impact of model uncertainties and methodological choices on the regionally attributed global-mean temperature increase. A climate assessment model has been developed to calculate changes in greenhouse gas concentrations, global-mean temperature and sea-level rise attributable to individual regions. The analysis shows the impact of the different choices in methodological aspects to be as important as the impact of model uncertainties on a region's contribution to present and future global temperature increases. Choices may be the inclusion of the anthropogenic non-CO2 greenhouse gas emissions and/or theCO2 emissions associated with land-use changes. When responsibility to global temperature change is attributed to all emitting Parties, the impacts of modeling uncertainties and methodological choices on contributions of individual Parties are considerable. However, if relative contributions are calculated only within the group of Annex I countries, the results are less sensitive to the uncertainty aspects considered here.

Climate change, potential evapotranspiration and moisture availability in the mediterranean basin

AbstractSimple methods for estimating potential evapotranspiration, requiring only temperature and day length data, are compared by reference to the results from the Penman method. A modification of the Blaney and Criddle method, in which the c parameter is calculated from seasonal regression equations with the mean monthly temperature as the independent variable, is proposed and tested. It is found to work sufficiently well in the area of interest, the Mediterranean Basin. For a network of 248 Mediterranean temperature stations, present‐day seasonal mean potential evapotranspiration is estimated by this method. Using the results from four equilibrium‐mode general circulation models, seasonal mean scenarios of potential evapotranspiration per 1°C rise in global mean temperature caused by the enhanced greenhouse effect are presented. Comparison of scenarios of the change in potential evapotranspiration and scenarios of the change in precipitation indicates an unfavourable shift in moisture availability due to the enhanced greenhouse effect, throughout the Mediterranean region.

Bias in the Global Mean Temperature Estimated from Sampling a Greenhouse Warming Pattern with the Current Surface Observing Network

Abstract Theoretical and modeling studies suggest that increasing greenhouse gases will cause the global mean temperature to rise a few degrees centigrade during the next century. Current global coupled GCMs have shown a distinct pattern of warming associated with this global mean rise. It is important to know how well our observing network will be able to capture the global mean temperature rise associated with this pattern if it occurs. The authors consider if a sampling bias exist as a result of the spatial distribution of observations as they are now located (1950–1979) when detecting a pattern of temperature change that should be typical of a warming due to increasing atmospheric CO2. The observations prove adequate to estimate the globally averaged temperature change associated with the pattern of CO2 warming from a general circulation model with a bias whose absolute value is generally less than 2%.

Greenhouse warming and the Eurasian biota: are there any lessons from the past?

Climate models predict a rise in global mean temperature of around 2–4°C by the end of the next century, with far greater rises in the high latitudes. Mean annual temperature rises of 6–8°C are predicted for 65°N, and as much as 10–12°C for above 70°N. There can be little doubt that such changes will have profound effects on boreal and arctic ecosystems, both through the temperature effects themselves and through associated changes in water balance. There is abundant evidence of climatic change in the high latitudes from the last 2.4 million years of the Quaternary. In a succession of glacial-interglacial cycles, high latitude temperatures seem to have fluctuated overall by about the same amount as is projected for the next century. Perhaps it is possible to use our knowledge of such past changes to understand what might happen to the high latitude ecosystems once the future greenhouse warming gets under way? There are many potential pitfalls in using data from the past to attempt to predict the future. In addition to the limitations in the data, there are also many important differences in the rate and setting of changes that should be borne in mind. With regard to climatic time-scale, the biogeographical patterns which we observe for the past are far more likely to represent equilibrium situations than those which we will observe in the future. Equilibrium data can itself be useful in that it provides indications of the distribution of climate conditions towards which the Earth will move. For example, it provides support for the notion that the climatic models are indeed correct in predicting that the strongest warming will occur in the high latitudes. Even following the relatively slow climate changes of the Quaternary high latitudes, there is abundant evidence of disequilibrium in tree species migrations, lasting for millennia in some cases. The survival of nearly all the high-latitude forms of plants and animals known from the Pleistocene fossil record—despite the repeated climatic fluctuations—may provide reassuring evidence of their future resilience. However, the extinctions of many large arctic mammals at around the time of the most recent warming phase may provide warning of what will occur in the future to certain species whose populations are already depleted by human activity. The exceptions to this pattern of gradual change are the sudden climatic shifts which have occurred in the North Atlantic region on several occasions during the late Quaternary. These may offer the closest analogues that we have to the effects of a future greenhouse warming on high-latitude plant and animal communities. It seems that some groups of organisms, such as insects, molluscs and water plants were able to respond rapidly to the climate warming, perhaps on the timescale of decades. However, tree populations were left far behind and took centuries or milennia to catch up with the changed climate, resulting in unfamiliar ecological scenarios in the mid and high latitudes.

Energy resources, CO 2 production and energy conservation

World fossil fuel reserves, historical and current rates of consumption are reviewed and estimates of indigenous lives in geographical regions are made. Rates of production and accomulations of carbon dioxide and other greenhouse gases in the atmosphere are calculated and correlations made with measured global mean temperatures and concomitant sea-level rises. It is concluded that, if present rates of global fossil-fuel consumptions continue unabated, the world's fossil-fuel store will be depleted by the year 2050. This would be accompanied by a substantial rise in global mean temperature. The effects of various protocols for the reductions of emissions are examined. It is concluded that there is no alternative than to cease the production and release into the atmosphere of the more damaging man-made greenhouse gases as soon as is practicably possible and to seek a sustained reduction in the rates of combustion of fossil fuels world-wide via energy management and conservation. This course of action will result in extending the time available for the development of a future renewable energy economy.

Solar cycle length, greenhouse forcing and global climate

THE recent rise in global-mean surface air temperature is widely thought to be the result of increasing atmospheric concentrations of greenhouse gases1–3, but there are discrepancies between the predicted response of the atmosphere to this radiative forcing and the observed temperature changes1–5. Solar irradiance fluctuations have been proposed as a possible explanation for these discrepancies, and various solar properties (for example, radius6, smoothed sunspot number7 or cycle length8) have been suggested as proxies for solar irradiance variations in the absence of direct data. Here we model the effects of a combination of greenhouse and solar-cycle-length forcing and compare the results with observed temperatures. We find that this forcing combination can explain many features of the temperature record, although the results must be interpreted cautiously; even with optimized solar forcing, most of the recent warming trend is explained by greenhouse forcing.

Implications for global warming of intercycle solar irradiance variations

FOLLOWING earlier studies1–6, attention has recently been directed again to the possibility that long-term solar irradiance variations, rather than increased greenhouse gas concentrations, have been the dominant cause of the observed rise in global-mean surface temperature from the mid-nineteenth century to the present. Friis-Christensen and Lassen7 report a high correlation (0.95; ref. 8) between the variable period of the '11-year' sunspot cycle and the mean Northern Hemisphere land surface temperature from 1865 to 1985. The Marshall Institute report9 concludes that '…the sun has been the controlling influence on climate in the last 100 years, with the greenhouse effect playing a smaller role." Here we explore the implication that such putative solar irradiance variations would have for global warming. Our results provide strong circumstantial evidence that there have been intercycle variations in solar irradiance which have contributed to the observed temperature changes since 1856. However, we find that since the nineteenth century, greenhouse gases, not solar irradiance variations, have been the dominant contributor to the observed temperature changes.

CETA: A Model for Carbon Emissions Trajectory Assessment

We present an economic growth and energy use model incorporating representations of greenhouse gas accumulation, global mean temperature rise, and the damage cost associated with this temperature rise. Under alternative assumptions about the damage cost function, we find optimal time paths of CO2 emissions control and associated optimal carbon taxes. Our work indicates that with plausible assumptions, an optimal carbon tax will rise over time, in contrast to the “hump-shaped” carbon taxes implied by CO2 reduction policies currently being discussed. Our work also suggests that the damage cost function would have to be both high and nonlinear in order to justify the general level of CO2 control and carbon taxes implied by these policies.

Other forms of environmental pollution

SynopsisThis paper discusses the four main invisible products of fossil fuel combustion: carbon dioxide, sulphur dioxide, nitric oxide and unburned hydrocarbons. If carbon exchanges between atmosphere, ocean and biosphere remain at their recent levels, the CO2 concentration in the atmosphere is likely to double later next century, with a possible rise in global mean temperatures of around 2°C resulting in significant changes in regional climates. The consequences are uncertain, but with adequate research, there should be time to develop the understanding necessary to guide future policies. Sulphur dioxide, acid rain and photochemical oxidants are a more pressing problem. Knowledge here is more complete, but still subject to considerable uncertainties that have an important bearing on the extent and rate of response of affected areas to reduction in acid deposition. However, from the year 2000 onwards, with the replacement of existing plant with nuclear power or new sulphur-free coal-burning technology, United Kingdom sulphur emissions will continue to decline at about twice the pace of their previous rise. Nitrogen oxides contribute to rain acidity, may have direct toxic effects on plants and, when accompanied by hydrocarbons, can generate ozone, itself a damaging pollutant. The chemistry of ozone production is, however, complex, such that intuitive control policies could be counter-productive.