Ecology The Earth’s Climate
by
Justin Schoof
  • LAST REVIEWED: 20 May 2019
  • LAST MODIFIED: 25 February 2016
  • DOI: 10.1093/obo/9780199830060-0143

Introduction

Climate science focuses on the behavior of the climate system, which consists of the atmosphere, the hydrosphere, the cryosphere, the lithosphere, and the cryosphere. Climate variability results from changes within and among these components as well as changes in their interactions. As such, the climate system exhibits substantive internal variability across scales of time and space. The climate system is also sensitive to changes in external forcing, which include long-term changes in the Earth’s orbital parameters as well as anthropogenic changes in atmospheric trace gas concentrations. Changes in both internal and external forcing can also be accompanied by complex feedbacks whereby initial forcings are either amplified (positive feedback) or suppressed (negative feedback) by subsequent climate system processes. Like all sciences, the tools of climate science are theory, observation, and modeling.

General Overviews

General overviews of the Earth’s climate are available at all readership levels. Introductory textbooks, such as Wallace and Hobbs 2006 and Aguado and Burt 2014 are used in many university classrooms and provide a good overview of both meteorology and climatology. These texts provide a basic foundation for understanding the Earth’s climate. Rohli and Vega 2013 focuses on climatology and its subfields and provides a clear distinction between meteorology and climatology. A broader perspective, which appropriately places contemporary and future climate in its historical context is provided by Ruddiman 2013. Given the rapid growth of both climate monitoring and climate modeling capabilities, climate assessments have become important mechanisms for establishing the state of the science. The key assessments have been those of the Intergovernmental Panel on Climate Change (IPCC), such as IPCC 2013, which provide regular updates on both large-scale and regional climate changes, as well as advancements in understanding of climate system processes in the context of past and future climate changes. National assessments, such as the United States National Climate Assessment (Melillo, et al. 2014) serve as a voice for the strong scientific consensus regarding the anthropogenic contribution to recent climate change and also address stakeholder interests in potential impacts of climate variability and change.

The History of Climate Science

Contemporary climate science is often considered to be a relatively new field, and indeed, until a few decades ago, most climatologists were tasked with computing averages of weather variables such as temperature and precipitation over long periods (greater than thirty years) to establish climate normals. However, climate science is approaching its two hundredth birthday, with the first paper about what is now known as the greenhouse effect written by Fourier 1824. The effects of anthropogenic carbon dioxide emissions on temperature were noted as early as the late 1930s by Callendar 1938, among others. Climate models were being used by the 1960s (see Sellers 1969), which also saw the first applications of complex models including feedbacks used to study the impact of changing greenhouse gas concentrations (e.g., Manabe and Wetherald 1967). Interestingly, the effects of increasing carbon dioxide were hypothesized and modeled before observations indicated that such increases had actually occurred. Keeling, et al. 1976 is widely credited with being the first study to provide observational evidence of an increase in atmospheric carbon dioxide. The so-called Keeling curve, which includes measurements from 1958 to present, now represents the longest instrumental record of atmospheric carbon dioxide. While tremendous strides have been made in understanding various aspects of climate system behavior since these early influential studies, most of their content is remarkably consistent with contemporary climate science perspectives. Many foundational contributions have been assembled into a single volume by Archer and Pierrehumbert 2011. Weart 2008 also provides an excellent overview of the history of climate science.

  • Archer, D., and R. Pierrehumbert. 2011. The warming papers: The scientific foundation for the climate change forecast. Hoboken, NJ: Wiley-Blackwell.

    Save Citation »Export Citation » Share Citation »

    The authors review key contributions to scientific foundation of contemporary climate science. Historically important papers are reproduced and supplemented with commentary about their role in understanding of climate change.

    Find this resource:

  • Callendar, G. S. 1938. The artificial production of carbon dioxide and its influence on climate. Quarterly Journal of the Royal Meteorological Society 64:223–240.

    DOI: 10.1002/qj.49706427503Save Citation »Export Citation » Share Citation »

    This is the first paper to estimate anthropogenic carbon emissions and suggest that such emissions were altering the Earth’s climate.

    Find this resource:

  • Fourier, J. B. F. 1824. On the temperatures of the terrestrial sphere and interplanetary space. Mémoires de l’Acedémie Royale des Sciences 7:569–604.

    Save Citation »Export Citation » Share Citation »

    This paper is widely acknowledged as the first to consider the energy balance of a planet as a key determinant of its temperature and therefore the first paper to describe what is now known as the greenhouse effect.

    Find this resource:

  • Keeling, C. D., R. B. Bacastow, A. E. Bainbridge, et al. 1976. Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii. Tellus 28:538–551.

    Save Citation »Export Citation » Share Citation »

    Keeling and colleagues present an eight-year record of carbon dioxide concentrations, presenting instrumental evidence of an increase of approximately 1 ppm per year. They also note the well-mixed nature of carbon dioxide by establishing the similarity between values observed in different regions.

    Find this resource:

  • Manabe, S., and R. T. Wetherald. 1967. Thermal equilibrium of the atmosphere with a given distribution of relative humidity. Journal of the Atmospheric Sciences 24:241–259.

    DOI: 10.1175/1520-0469(1967)024<0241:TEOTAW>2.0.CO;2Save Citation »Export Citation » Share Citation »

    This is the first paper to consider the thermal effects of increasing carbon dioxide. Of particular importance here is the quantification of the role of water vapor, which provides a strong feedback to greenhouse gas induced warming.

    Find this resource:

  • Sellers, W. D. 1969. A global climatic model based on the energy balance of the earth-atmosphere system. Journal of Applied Meteorology 8:392–400.

    DOI: 10.1175/1520-0450(1969)008<0392:AGCMBO>2.0.CO;2Save Citation »Export Citation » Share Citation »

    This was one of the first papers to use an energy balance model to describe the Earth’s climate. Sellers focus is on estimating the role of changes in the solar constant, the surface albedo, and atmospheric greenhouse gas concentrations.

    Find this resource:

  • Weart, S. R. 2008. The discovery of global warming. Cambridge, MA: Harvard Univ. Press.

    DOI: 10.4159/9780674417557Save Citation »Export Citation » Share Citation »

    Weart provides an excellent overview of how global warming rose to prominence over the past few decades. Special attention is given to the scientific history of global climate change and the role of politics in the development of climate science.

    Find this resource:

Observations and Data

The key role of environmental monitoring in understanding climate variability and change has led to the recognition of observations as a critically important aspect of climate science. Climate has traditionally been studied using time series of variables measured at weather stations. Such series are sensitive to station moves, changes in instrumentation, or changes in siting (e.g., urbanization), which can undermine data homogeneity and influence trend detection and attribution. An excellent overview of homogeneity issues and correction methods is provided by Peterson, et al. 1998. While station-based networks remain critically important for climate monitoring, satellite-derived climate information has played an increasingly important role in nearly all aspects of climate science, from snow extent monitoring to air quality. Qu, et al. 2013 provides a nearly comprehensive overview of applications of satellite data in the study of global change. For the study of large-scale variations in climate (e.g., atmospheric circulation), data from multiple sources are assimilated into a model, which then produces gridded (usually at around two degree resolution) fields of multiple variables at multiple levels that are constrained by the available observations but have the advantage of being spatially and serially complete. These so called reanalysis data products have now been developed independently by research groups across the globe; the most widely utilized (and cited) products have been developed in the United States by the National Center for Environmental Prediction and National Center for Atmospheric Research (Kalnay, et al. 1996). The wider use of climate models has also led to greater coordination with respect to experimental design and data availability. A primary example of such coordination is the 5th Phase of the Coupled Model Intercomparison Project (CMIP5; Taylor, et al. 2012), which provided the basis for the most recent reports of the Intergovernmental Panel on Climate Change. The volume of available climate data is rapidly growing along with the number of people using climate data for decision-making. Overpeck, et al. 2013 broadly describes types of climate data that are available, while offering a framework for provision of data in the coming decades. A small number of journals also specialize in issues related to measurement and data, with the Journal of Atmospheric and Oceanic Technology being a key example.

Modeling

Given the urgent need to understand the current climate in the context of the past and to develop projections of future climate, modeling of the climate system has become increasingly important in recent decades. The most widely utilized models are three-dimensional (four-dimensional, if time is considered) models of the coupled climate system. Such models represent the known drivers of climate variability and change (albeit in simplified form) and are among the most complex models being utilized in any scientific field. Excellent overviews of coupled modeling are provided by Washington and Parkinson 2005 and Trenberth 2010. Much of the modeling conducted in recent years has been undertaken as part of coordinated modeling experiments, such as the 5th Phase of the Coupled Model Intercomparison Project (CMIP5; Taylor, et al. 2012). Along with advances in modeling has come the need for evaluation of model strengths and weaknesses. While these are often conducted on a regional basis and for specific types of applications, some broad overviews of climate model performance are available in the literature (e.g., Flato, et al. 2013). The need for climate change information at scales smaller than those resolved by global models has led to development of regional modeling approaches, either by further dynamical downscaling (i.e., nesting a high resolution model within a global climate model over a smaller domain; see Giorgi 2006) or by applying statistical post-processing, often referred to as statistical downscaling (see the review by Schoof 2013). Several journals also focus on, or publish a large number of papers related to, climate modeling. Noteworthy among these journals are Climate Dynamics and Journal of Climate.

Paleoclimate

Understanding the climate of the past is key to understanding contemporary and potential future climates. The lack of historical instrumental records beyond the last century has led to the development of climate histories based on proxy data, such as tree rings, deep sea sediments, and ice cores. Climate models are also used, often in conjunction with proxy data, to better understand past climates. Ruddiman 2013 is a very readable overview of Earth’s climate history as well as the science underlying various climate proxies and other tools used to investigate the Earth’s past climate. A key focus of paleoclimate is understanding climate system evolution during and since the last glacial maximum. Weaver, et al. 1998 presents a view of the last glacial maximum in terms of forcing from carbon dioxide, orbital variations, and the ice sheets themselves. Proxy data from the last glacial maximum have also been helpful in approximating the climate sensitivity (the change in temperature associated with a doubling of atmospheric carbon dioxide) as in Manabe and Broccoli 1985. A review of work related to the deglaciation of the northern hemisphere at the end of the last glacial maximum is described by Alley and Clark 1999. With the exception of the last 150 years, the climate of the last ten thousand years has been remarkably stable, especially outside of the tropics. Mann and Jones 2003 presents a controversial, but largely upheld, record of global temperatures of the last two millennia. The authors’ results strongly suggest that recent temperatures in the northern hemisphere are the warmest during that period. Masson-Delmotte, et al. 2013 provides a comprehensive overview of paleoclimate studies as they relate to our understanding of current and future climate. Several journals, such as Climate of the Past and Palaeogeography, Palaeoclimatology, Palaeoecology, focus on understanding past climates as they relate to environmental indicators.

  • Alley, R. B., and P. U. Clark. 1999. The deglaciation of the Northern Hemisphere: A global perspective. Annual Reviews of Earth and Planetary Sciences 27:149–182.

    DOI: 10.1146/annurev.earth.27.1.149Save Citation »Export Citation » Share Citation »

    This paper provides an overview of the global conditions associated with the most recent northern hemisphere deglaciation, which was induced by orbital variations, but reinforced by multiple feedbacks within the climate system.

    Find this resource:

  • Climate of the Past. 2005–.

    Save Citation »Export Citation » Share Citation »

    This open access journal includes papers on all topics related to past climate.

    Find this resource:

  • Manabe, S., and A. J. Broccoli. 1985. A comparison of climate model sensitivity with data from the last glacial maximum. Journal of the Atmospheric Sciences 42:2643–2651.

    DOI: 10.1175/1520-0469(1985)042<2643:ACOCMS>2.0.CO;2Save Citation »Export Citation » Share Citation »

    Manabe and Broccoli use two models to investigate the climate of the last glacial maximum. The models differ in terms of how clouds are modeled, yet the results are similar for most aspects of the glacial climate. This paper was instrumental in advancing climate modeling as applied to paleoclimate problems.

    Find this resource:

  • Mann, M. E., and P. D. Jones. 2003. Global surface temperatures over the past two millennia. Geophysical Research Letters 30:1820.

    DOI: 10.1029/2003GL017814Save Citation »Export Citation » Share Citation »

    Mann and Jones use proxy data to reconstruct hemispheric and global near-surface air temperature over the past two millennia. They find that the northern hemisphere is currently warmer than any other time in the previous two millennia. Southern hemisphere proxy data are relatively sparse and preclude the authors from making a similar statement about the planet as a whole.

    Find this resource:

  • Masson-Delmotte, V., M. Schulz, A. Abe-Ouchi, et al. 2013. Information from paleoclimate archives. In Climate change 2013: The physical science basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by T. F. Stocker, D. Qin, G. -K. Plattner, et al. Cambridge, UK: Cambridge Univ. Press.

    Save Citation »Export Citation » Share Citation »

    This chapter from the most recent report of the Intergovernmental Panel on Climate Change focuses on information derived from proxies and modeling simulations but with the primary goal of contextualizing recent climate changes.

    Find this resource:

  • Palaeogeography, Palaeoclimatology, Palaeoecology. 1965–.

    Save Citation »Export Citation » Share Citation »

    This journal focuses broadly on paleoenvironmental studies, including interdisciplinary studies related to paleoclimate.

    Find this resource:

  • Ruddiman, W. F. 2013. Earth’s climate: Past and future. 3d ed. New York: Freeman.

    Save Citation »Export Citation » Share Citation »

    An overview of factors governing climate across the timescales comprising the entirety of Earth’s 4.6 billion year history. Ruddiman describes tectonic and orbital effects on climate as well as deglacial, millennial, and historical changes. This book places contemporary climate change within the context of natural climate variability. Also see General Overviews.

    Find this resource:

  • Weaver, A. J., M. Eby, A. F. Fanning, and E. C. Wiebe. 1998. Simulated influence of carbon dioxide, orbital forcing, and ice sheets on the climate of the last glacial maximum. Nature 394:847–853.

    DOI: 10.1038/29695Save Citation »Export Citation » Share Citation »

    This paper was among the first to investigate the last glacial maximum using a numerical model of the coupled climate system (atmosphere, oceans, and sea ice). The results suggest much cooler tropical temperatures relative to the current climate and a much cooler North Atlantic Ocean resulting from a weakened thermohaline circulation.

    Find this resource:

Future Climate

A key focus of climate science is development of future climate projections. The future climate is sensitive to both natural climate variations as well as external forcing, with the former related primarily to variations in coupled modes of atmosphere-ocean variability and the latter related primarily to changes in atmospheric greenhouse gas concentrations, resulting largely from anthropogenic activities. Changes in radiative forcing from greenhouse gases are largely related to changes in socioeconomic factors, such as population growth, economic growth and disparity, and adoption of new technology and renewable energy resources. For this reason, simulations of future climate must be predicated on assumptions about how greenhouse gas concentrations will evolve in the coming decades and the results exhibit strong sensitivity to these assumptions. Nevertheless, current science reflect an expectation of substantial warming, accompanied by an increase in the frequency and intensity of extreme events under continued warming this century. The most recent coordinated model experiment (CMIP5) adopted the representative concentration pathway approach described by Moss, et al. 2010 and extended by van Vuuren, et al. 2011. The key references on future climate and the comprehensive reports developed by climate scientists under the auspices of the Intergovernmental Panel on Climate Change (IPCC 2013; IPCC 2014a; IPCC 2014b), which focus on physical science, impacts and adaptation, and mitigation, respectively. A number of high impact journals now focus exclusively on climate change (e.g., Nature Climate Change, Climatic Change) while traditional high impact climate science journals, such as Journal of Climate, now devote substantive space to studies focused on climate change.

  • Climatic Change. 1977–.

    Save Citation »Export Citation » Share Citation »

    This journal focuses exclusively on problems related to climate variability and change. The content includes papers on physical climatology as well as impacts, adaptation, vulnerability, and mitigation.

    Find this resource:

  • Intergovernmental Panel on Climate Change. 2013. Climate change 2013: The physical science basis: Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by T. F. Stocker, D. Qin, G.-K. Plattner, et al. Cambridge, UK: Cambridge Univ. Press.

    Save Citation »Export Citation » Share Citation »

    This comprehensive report describes the current state of climate science with a focus on changes in climate system components and their interactions, understanding current and future climate in the context of the past, relating current and future climate to natural and anthropogenic forcing, and developing and presenting projections of future climate. Also see General Overviews.

    Find this resource:

  • Intergovernmental Panel on Climate Change. 2014a. Climate change 2014: Impacts, adaptation, and vulnerability. Part A, Global and sectoral aspects: Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by C. B. Field, V. R. Barros, D. J. Dokken, et al. Cambridge, UK: Cambridge Univ. Press.

    Save Citation »Export Citation » Share Citation »

    This comprehensive report focuses on identifying changes in risks and benefits in a world characterized by changes in climate and how any negative consequences might be addressed through adaptation and reduction of vulnerability.

    Find this resource:

  • Intergovernmental Panel on Climate Change. 2014b. Climate change 2014: Mitigation of climate change: Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by O. Edenhofer, R. Pichs-Madruga, Y. Sokona, et al. Cambridge, UK: Cambridge Univ. Press.

    Save Citation »Export Citation » Share Citation »

    The comprehensive report assesses the current literature on all aspects of climate change mitigation, ranging from scientific and technological developments and environmental, economic, and social considerations. Without recommending specific mitigation options, the report discusses options across levels of governance.

    Find this resource:

  • Journal of Climate. 1988–.

    Save Citation »Export Citation » Share Citation »

    This journal publishes papers on wide range of topics but focuses on large-scale climate variability and climate simulation and prediction. A large number of the papers published deal with some aspect of future climate.

    Find this resource:

  • Moss, R. H., J. A. Edmonds, K. A. Hibbard, et al. 2010. The next generation of scenarios for climate change research and assessment. Nature 463:747–756.

    DOI: 10.1038/nature08823Save Citation »Export Citation » Share Citation »

    This paper describes the trajectories of climate forcing used in the most recent coordinated climate experiments (Phase 5 of the Coupled Model Intercomparison Project; CMIP5).

    Find this resource:

  • Nature Climate Change. 2011–.

    Save Citation »Export Citation » Share Citation »

    This journal publishes high impact papers on climate change from both the physical and social sciences and specializes in interdisciplinary approaches to scientific problems.

    Find this resource:

  • van Vuuren, D. P., J. Edmonds, M. Kainuma, et al. 2011. The representative concentration pathways: an overview. Climatic Change 109:5–31.

    DOI: 10.1007/s10584-011-0148-zSave Citation »Export Citation » Share Citation »

    This paper was a follow-up to Moss, et al. 2010 that extends their description of the representative concentration pathway scenarios.

    Find this resource:

Climate Data Sources

Given advances in computation and communication in the last decade, free climate data are now widely accessible for most regions. Most of these data are derived from land-based stations, moored or floating buoys, radiosondes (weather balloons), satellites, and numerical models. The US National Center for Environmental Information is the clearinghouse for a large collection of climate data, including many global products as well as some paleoclimate data. The European Climate Assessment also provides a large collection of climate data, including daily data and also summaries of extremes and other climate descriptors. Climate model data are now widely available, with data from the Intergovernmental Panel on Climate Change (IPCC) report available at online. The complexity of contemporary climate models results in spatial resolution that is often insufficient for impacts related work, including some applications in ecology. For that reason, climate projections are often first downscaled to provide credible spatial patterns, especially in areas of substantial relief. Some downscaled projections have been made available for free download, such as the Bias Correction and Spatial Disaggregation data developed for the United States.

Climate and Ecology

The strong two-way linkages between terrestrial vegetation and climate have led to the development of the subfield of ecological climatology. Because vegetation is a key component of the carbon cycle, any changes in land cover or productivity have consequences for carbon storage in other climate system reservoirs. An excellent overview of this field is provided by Bonan 2008. A large number of studies have focused on impacts of climate change on terrestrial ecology, including widely cited contributions from Walther, et al. 2002 and Parmesan and Yohe 2003 and a comprehensive review by Parmesan 2006. Much of the ecological climatology research is rooted in studies of phenology and an excellent survey of this topic is provided by Schwartz 2013. Smith 2011 presents a definition for an extreme climatic event in an ecological context and provides a framework for ecological research related to impacts of climate extremes.

back to top

Article

Up

Down