Climate Change Science: A Modern Synthesis

Global warming involves a temperature change on planet Earth. The temperature is climbing gradually so that the average person does not feel it. However, there are indirect lines of evidence that the average person can see and feel. Increasing unusual weather patterns reported by the news media nearly every day indicate climate change. More floods in parts of the world and more intense droughts in others indicate climate change. Fires raging in some areas and unusual snowfalls in others indicate climate change. A season of intense tornados and more intense hurricanes indicates more energy in the atmosphere and that is climate change. As the Earth’s global temperature increases, rates of evaporation also increase placing more water in the atmosphere. More evaporation dries out the land, soils, forests and takes more water from the ocean. All are signs of a changing climate. A warming Earth is climate change and it is affecting everyday life throughout the globe. Thus ‘global warming’ is used to refer to Earth’s gradually increasing temperature.

An introduction is given to scientific principles including the laws of thermodynamics and the differences between natural laws, hypotheses, and theories. The concept of geologic time is introduced with examples given of the age of the Earth, the time it takes for climate to change, and examples from the geologic record. Scientific notation is described with examples from very large and very small numbers. Some of the jargon used by climate change scientists is defined. Some early scientists are named from Pliny the Elder to Karl Popper along with their main contributions. Chaos theory is introduced as is the “butterfly effect.” The concept of multiple working hypotheses is explained.

The scientific method is not a linear one-dimensional sequence of events but a three-dimensional approach to solving problems and obtaining answers to questions. A description of the scientific method and examples are given in this chapter. An understanding of the scientific method (or methods) is necessary in order to gain an insight into, and to hopefully gain some appreciation for, what most scientists do and the way they do it, so this chapter deals with the scientific method and how some important scientists have used it to achieve their results. The emphasis is on climate science and climate scientists but other important scientists are mentioned and their results given. Newton’s laws of motion are described and their relationship to climate change is given. Continental drift is introduced and related to climates of the past.

Earth’s energy imbalance is the difference between the amount of solar energy absorbed by the Earth and the amount of energy it radiates to space as heat. If the imbalance is positive, more energy coming in than going out, we can expect Earth to become warmer. If the imbalance is negative, then more energy is going out than is being received and the Earth will cool. Earth’s energy imbalance is the single most crucial measure of the status of Earth’s climate and it defines expectations for future climate change. The Earth’s energy budget is explained in this chapter and the fact that Earth retains more of the electromagnetic radiation incident upon it from the Sun than it radiates back to space. The solar constant and aspects of solar electromagnetic radiation and the electromagnetic spectrum are discussed and illustrated. A distinction between weather and climate is made. Calculations of Earth’s temperature with and without an atmosphere are completed. Earth’s radiation laws are defined. The outgoing spectral radiance at the top of Earth’s atmosphere and the absorption at specific frequencies by greenhouse gases are illustrated.

Global warming started when humans began altering the chemistry of the atmosphere by agricultural practices about 10,000 years ago and was exacerbated by the beginning of the Industrial Revolution due to the increased burning of coal as a cheap source of energy. As a result of these factors, and the mass production of the internal combustion engine, greenhouse gases have been building up in the atmosphere for the past 10,000 years. There are certain observable trends that are and have been taking place, especially during the latter half of the twentieth century and into the twenty-first. Among these are rising temperatures over land and sea, receding glaciers and rising sea level. Other climate change trends are listed and further discussed in this chapter. Different temperature scales used in climate science are Celsius, Fahrenheit, and Kelvin. The features of temperature graphs are explained and examples given. A typical meteorological station is described and illustrated. Sources of temperature data are discussed as well as potential problems with the data. The BEST study, their reasons, and their results are explained as are methane clathrates and climate change perturbations and attribution.

The Earth is getting warmer and the surface temperature reflects the warming trend. Temperature records are kept and analyzed by several government agencies throughout the world among which are the Goddard Institute of Space Studies in the U. S., the Climate Research Unit in the U. K., the Japan Meteorological Association, and others. Tipping points beyond which nothing can be done to reverse them are discussed. Work by the U.K.’s Met Office and the Climate Research Unit of the University of East Anglia was one of the first to report global warming. James Hansen of GISS reported on their studies and appeared before a committee of the U. S. congress advocating that action be taken to slow or stop warming that was occurring due to greenhouse gases. Scenarios A, B, and C were described by Hansen. Hansen and Lebedeff’s paper defining a method of determining a global average temperature is described as is the current method of determination.

Climate change science is a part of Earth science. One cannot study the Earth and not study climate; and climate is changing throughout the globe. Weather is also changing and the study of weather is also part of Earth science. The faint early Sun paradox is discussed and some of the early evidence from the geologic past is presented. The four premises of the Gaia hypothesis or theory are given and reasons are stated for and against the hypothesis or theory. The Great Oxygenation Event is introduced with the role of cyanobacteria in the early Earth atmosphere. There are different kinds of ways to conduct scientific work and these are discussed. Examples of good science, bad science, and non-science are given. Different scales and their importance are discussed. Fractals are introduced.

The Earth’s atmosphere is a thin envelope of gases surrounding the solid planet, the hydrosphere, and biosphere. The composition of the atmosphere consists largely of two elements, oxygen and nitrogen. The atmosphere also contains chemicals which absorb heat from the Earth’s surface and radiate it in all directions including back to the surface. This results in the greenhouse effect that keeps the planet warm enough to sustain life. The greenhouse gases include water vapor, carbon dioxide, and methane. Carbon dioxide is the main greenhouse gas of concern today as it is increasing rapidly in the atmosphere largely as the result of the burning of fossil fuels. The Keeling curve shows the steady increase in carbon dioxide since 1958. Different zones of the atmosphere are defined. The effects of Arctic warming are causing changes in the Jet Stream. These changes are affecting weather patterns and weather uncertainty is increasing. The isotopes of carbon are listed and the significance of carbon-14 (¹⁴C) is explained with reference to carbon dioxide from fossil fuels.

The physical and chemical properties of carbon dioxide are essential for the existence of humankind on Earth because of its role in the greenhouse effect. Water vapor, methane, and nitrous oxide are also important greenhouse gases as they help keep the planet warm. The carbon cycle is important for life on Earth because life is carbon based. An illustration in this chapter shows how carbon moves through the environment. Sources and sinks of several of the greenhouse gases are discussed. The ozone hole is discussed with its ramifications for causing harm to life forms. Global Warming Potentials (GWPs) are defined relative to CO₂. Other greenhouse gases are discussed.

Albedo is defined as the degree of reflectivity of a substance. Albedo values are given for common Earth substances. Radiative forcing of the climate system is introduced and the relative forcings by principal substances are given. Earth’s energy is received mainly from the Sun and is received at the top of the atmosphere. This solar radiation cascades through the atmosphere which acts as a transparent window through which most of the radiation is allowed to pass. The Sun radiates energy as a blackbody that appears very bright due to its very high temperature. Most matter acts as a blackbody and radiates energy dependent on its temperature. The Earth’s moon is a relatively low temperature blackbody and we see its radiation as moonlight. The changing climate (global warming) is due mainly to the cascading energy scenario but the climate is also responsive to energy within the Earth.

Earth’s atmosphere, made up essentially of the gases that surround our planet, consists of circulation patterns that move air from one place to another and from the surface to higher elevations. There are lateral and vertical ways to force air to move and these are explained in this chapter. The Coriolis Effect, as well as its effect on atmospheric circulation, is explained. Trade winds, polar highs, westerlies, easterlies, doldrums, and horse latitudes are explained and illustrated. Air movement over the Western Hemisphere is illustrated. The Intertropical Convergence Zone (ITCZ) and Horse Latitudes as well as Hadley, Polar, and Ferrel cells are explained and illustrated. The dangers of increased energy and uncertainty concerning future weather events are discussed. Some extreme weather events occurring during 2011–2012 are enumerated and explained in the context of changing climatic conditions (i.e., the “new normal”).

Oceans cover about 71% of Earth’s surface. There are five ocean basins that are interconnected by circulation and are separated by continental land masses except for the Southern Ocean. Ocean water is surprisingly uniform; at least as far as near-surface waters are concerned. Ocean circulation is caused by atmospheric circulation, temperature differences, bottom configuration, and salinity differences. Ocean acidification, one very important aspect of rising carbon dioxide levels, is explained. Dying coral reefs and shell-baring organisms and the effects of rising carbon dioxide levels on oceans are discussed. Ocean acidification is one of the main results of carbon dioxide buildup in the atmosphere.

Ocean heat is increasing, especially in the upper 700 m and sea level is rising worldwide. A worldwide rise in sea level is known as a eustatic sea level rise. Factors affecting climate are complex but El Niño and La Niña are well established. Together they form the ENSO, or El Niño (and La Niña) Southern Oscillation in the equatorial Pacific that affects weather worldwide. Wetlands are an important ecosystem and many are being lost as a result primarily of sea level rise but because of other activities and influences by humankind as well.

The cryosphere consists of glacial ice, sea ice, ice shelves, ice caps, continental glaciers, valley glaciers, permafrost, and ice in rivers and lakes. Some of the cryosphere is temporary, such as sea ice near the North Pole and elsewhere, and it melts in warm months and re-freezes during colder months. Glacial ice on land represents a vast store of fresh water. It also is directly tied to sea level. For example, as glacial ice melts, sea level is raised worldwide. As glaciers expand, sea level is lowered worldwide. The two most important areas on Earth for freshwater storage are Greenland and Antarctica. Greenland’s glaciers are receding faster than Antarctica’s because global warming is affecting the Northern Hemisphere glaciers more so than those in the Southern Hemisphere. Sea ice is disappearing in the Northern Hemisphere and is sometimes expanding in the Southern Hemisphere. The rate of Greenland’s ice loss is accelerating. Ice cores from the cryosphere tell scientists a great deal about the history of the atmosphere from gas bubbles trapped within them. Isotope studies tell us about past atmospheric compositions and temperatures. Glaciers were more extensive in the recent geologic past in what is generally known as the Pleistocene “ice age.” Carbon dioxide and global temperatures have been correlated throughout the past 800,000 years from ice cores.

Permafrost is defined as permanently frozen ground, except the upper part usually thaws during summer months. Most of the permafrost on Earth is in areas that were glaciated during the last ice age and are still cold enough to keep the ground frozen. There is a tremendous quantity of methane trapped in permafrost that is being released as the permafrost melts. Methane is 25 times more potent as a greenhouse gas than carbon dioxide, to which it eventually converts in the atmosphere. Methane clathrates are potentially the cause of relatively sudden climate changes in the geologic past (PETM) and today represent a potential clathrate gun hypothesis for future sudden climate change.

Continents and ocean basins make up the planet’s crust, Earth’s outermost layer. Continental areas consist of sialic materials and ocean basins consist of simatic materials, the two main rock types, based on their mineral composition, that make up the Earth’s crust. There are several models for naming continents including a seven-continent model and a three-continent model. Both continents and ocean basins have mountain ranges and the continental ones, such as the Alps, Himalayas, Appalachians, and Rockies are better known. The Mid-Atlantic Ridge is most likely the best-known oceanic one. Continental climates are moderated by nearby bodies of water and often form rain-shadows. The continents have drifted to their present locations from a supercontinent called Pangaea that straddled the equator at times past. The mechanism for drifting continents is the concept of Harry Hess’ sea-floor spreading that gave rise to the theory of plate tectonics.

There are different criteria used to classify climates. The most common classification is the Köppen-Geiger classification that recognizes five major climatic zones: Tropical, Dry, Moderate (or Temperate), Continental, and Polar with subzones under each. Classifications of climate systems include those based on their origin or those based on their effects. The Bergeron classification is based on areas of origin for air masses. Thornthwaite devised a climate classification built on the physical interactions between local moisture and temperature. Disruption of climate and of the Jet Stream in the Northern Hemisphere due to arctic warming and sea ice melting is a concern.

Climate models range in complexity from very simple to very complex. General Circulation Models are the most complex and most require time on a supercomputer in order to utilize all the required data. Box models, Energy Balance models, Radiative-Convective models, and General Circulation models are all used to allow scientists to vary input and ask “what if” questions about the climate system. Validation of models is necessary in order to have confidence in modeling and for individual models. History matching (or hindcasting) is an integral part of the modeling process. The validation process allows scientists to have greater confidence in model results.

Paleoclimatology is the study of climates of the past. This study uses historical records, direct lines of evidence, and proxies to determine past climates. As we go back in time from the present, the less confidence we have in the data, so paleoclimatologists rely on converging data paths to increase confidence in the results and conclusions. Ice cores tell scientists a great deal about the ancient composition of the atmosphere by analyzing the air bubbles contain within them. These air bubbles within the ice contain samples of the atmosphere at the time they formed. Stable isotopes from ice and sediment samples reveal temperature data by proxy. Pollen, tree rings, coral growth, cave deposits, assemblages of organisms hold clues to past climates.

Scientists know the most about the most recent climate changes and events. The more time that passes, the less we know about Earth history. We know more about climate changes in the Holocene than we do in the Pliocene; more about the Pleistocene than the Paleocene. We know more about the Wisconsin glaciation than we know about the Kansan, and more about the Kansan that the Nebraskan. The Tibetan Plateau began to be uplifted with the collision of the Indian Plate with the Eurasian plate about 58 million years ago and began to affect the climate of Southeast Asia. The high standing plateau and the Himalayan Mountains caused the severe monsoons that affect the area today.

Abstract

The Pleistocene glaciations are unique in geologic history as far as is known at present. The periodicity appears to be the result of the interaction of Milankovitch cycles and carbon dioxide. The 100,000 year cycles appear to have initiated the major glacial advances and carbon dioxide releases, perhaps as methane, appear to have resulted in interglacial episodes. As glaciers advanced, ocean and atmospheric currents were affected and carbon dioxide levels were lowered. As glaciers retreated, ocean and atmospheric currents returned to their previous paths and carbon dioxide levels increased. In order to place the periodicity of the Pleistocene in the proper time perspective, climate conditions leading up to the Pleistocene are outlined in this chapter.

Climate projections are not the same as climate predictions. Climate change scientists can’t predict the future but with knowledge of past climates and detected climate trends, it is feasible to project climate change into the future using various scenarios. The IPCC did several projections in their AR4 2007 report and these are discussed in this chapter. What will happen in a hotter, flatter, and more crowded world is something inhabitants of this planet should be concerned about. There are conditions that we can be fairly confident about as we gaze into a virtual future. The political climate is separate from the temperature but has a great deal to do with the future of Earth and its inhabitants. Some politicians are famous or notorious for their stance on climate change and their contribution to environmental issues (both positive and negative) and some are discussed in this and the following chapters. Mitigation of climate change is to slow things down and thereby improve the global temperature rise or to stop it entirely. Is it already too late to stop the globe from further warming and, if it is not, what should or can we do?

At its heart, climate denial is the rejection of the scientific consensus that humans are disrupting the climate. Denial of a consensus can be identified by five telltale characteristics: fake experts, cherry picking, logical fallacies, impossible expectations and conspiracy theories. These techniques are observed in the tactics and strategies of the climate denial movement, disseminated by ideological think-tanks, some conservative governments and vested interests through a range of media streams. The key to responding to climate misinformation is to provide alternative narratives that are more compelling than the myths they replace.

Virtually all climate misinformation can be divided into five categories: fake experts, cherry picking, logical fallacies, impossible expectations and conspiracy theories. The most common climate myths are grouped into these five categories, examining the rhetorical techniques employed to mislead and explaining the science that puts the myths in proper context.