9.5: Anthropogenic Causes of Climate Change - Biology

9.5: Anthropogenic Causes of Climate Change - Biology

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As shown in the previous section, prehistoric changes in climate have been very slow. The climate changes observed today are rapid and largely human-caused. Evidence shows that climate is changing, but what is causing that change? Scientists have suspected since the late 1800s that human-produced (anthropogenic) changes in atmospheric greenhouse gases would likely cause climate change, as changes in these gases have been the case every time in the geologic past. By the middle 1900s, systematic measurements began which confirmed that human-produced carbon dioxide was accumulating in the atmosphere and other earth systems, like forests and the oceans. By the end of the 1900s and into the early 2000’s the Theory of Anthropogenic Climate Change was solidified as evidence from thousands of ground-based studies and continuous satellite measurements of land and ocean mounted in number revealing the expected temperature increase. Theories evolve and transform as new data and new techniques become available, but they represent the state of thinking for that field. The Theory of Anthropogenic Climate Change is that humans are causing most of the current changes to climate by burning fossil fuels such as coal, oil, and natural gas. This section summarizes the scientific understanding of anthropogenic climate change.

Scientific Consensus

The overwhelming majority of climate studies indicate that human activity is causing rapid changes to the climate, which will cause severe environmental damage. There is a strong scientific consensus on the issue. Studies published in peer-reviewed scientific journals show that 97 percent of climate scientists agree that climate warming is from human activities [52]. There is no alternative explanation for the observed link between human-produced greenhouse gas emissions and the changing modern climate. Most leading scientific organizations endorse this position, including the U.S. National Academy of Science which was established in 1863 by an act of Congress under President Lincoln. Congress charged the National Academy of Science “with providing independent, objective advice to the nation on matters related to science and technology” [53]. Therefore, the National Academy of Science is the leading authority when it comes to policy advice related to scientific issues.

One way we know that the increased greenhouse gas emissions are from human activities is with isotopic fingerprints. For example, fossil fuels have a ratio of stable carbon-13 to carbon-12 (13C/12C) that is different from today’s stable carbon ratio in the atmosphere. Studies have been using isotopic carbon signatures to identify anthropogenic carbon in the atmosphere since the 1980s. Isotopic records from the Antarctic Ice Sheet show stable isotopic signature from ~1000 AD to ~1800 AD and a steady isotopic signature gradually changing since 1800 followed by rapid change after 1950. These changes show the atmosphere having a carbon isotopic signature increasingly more similar to that of fossil fuels [42; 54].

Anthropogenic Sources of Greenhouse Gases

Anthropogenic emissions of greenhouse gases have increased since pre-industrial times due to global economic growth and population growth. Atmospheric concentrations of the leading greenhouse gas, carbon dioxide, are at unprecedented levels that haven’t been observed in at least the last 800,000 years [6]. The pre-industrial level of carbon dioxide was at about 278 parts per million (ppm). As of 2016, carbon dioxide was, for the first time, above 400 ppm for the entirety of the year. Measurements of atmospheric carbon at the Mauna Loa Carbon Dioxide Observatory show a continuous increase since 1957 when the observatory was established from 315 ppm to over 410 ppm in 2017. The daily reading today can be seen at Daily CO2. Based on the ice core record over the past 800,000 years, carbon dioxide ranged from about 185 ppm during ice ages to 300 ppm during warm times [52]. View the data-accurate NOAA animation below of carbon dioxide trends over the last 800,000 years.

Figure (PageIndex{1}): Total anthropogenic greenhouse gas (GHG) emissions from economic sectors in 2010. The circle shows the shares of direct GHG emissions (in % of total anthropogenic GHG emissions) from five economic sectors in 2010. The pull-out shows how shares of indirect CO2 emissions (in % of total anthropogenic GHG emissions) from electricity and heat production are attributed to sectors of final energy use. AFOLU is agriculture, forestry, and other land use (Source: Pachauri et al. 2014).

What is the source of these anthropogenic greenhouse gas emissions? Fossil fuel combustion and industrial processes contributed 78% of all emissions since 1970. Sectors of the economy responsible for most of this include electricity and heat production (25%); agriculture, forestry, and land use (24%); industry (21%); transportation including automobiles (14%); other energy production (9.6%); and buildings (6.4%) [6]. More than half of greenhouse gas emissions have occurred in the last 40 years (Figure 1.5 p.45 of [6] and 40% of these emissions have stayed in the atmosphere. Unfortunately, despite scientific consensus, efforts to mitigate climate change require political action. Despite the growing amount of climate change concern, mitigation efforts, legislation, and international agreements have reduced emissions in some places, yet the continued economic growth of the less developed world has increased global greenhouse gas emissions. In fact, the time between 2000 and 2010 saw the largest increases since 1970 [6].

Figure (PageIndex{1}): Annual global anthropogenic carbon dioxide (CO2) emissions in gigatonne of CO2-equivalent per year (GtCO2/yr) from fossil fuel combustion, cement production and flaring, and forestry and other land use, 1850–2011. Cumulative emissions and their uncertainties are shown as bars and whiskers.


6. Pachauri, R. K. et al. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. (IPCC, 2014).

42. Weissert, H. Deciphering methane’s fingerprint. Nature 406, 356–357 (2000).

52. National Oceanic and Atmospheric Administration. ESRL Global Monitoring Division - Global Greenhouse Gas Reference Network. (2005). Available at: (Accessed: 14th September 2016)

53. National Academy of Sciences. Mission Statement. (2016). Available at: (Accessed: 3rd August 2016)

54. Francey, R. J., Allison, C. E., Etheridge, D. M., Trudinger, C. M. & others. A 1000‐year high precision record of δ13C in atmospheric CO2. Tellus B Chem. Phys. Meteorol. (1999).

Global Climate Change: What You Need to Know

Record floods. Raging storms. Deadly heat. Climate change manifests itself in myriad ways, and it’s the ultimate equalizer: a challenge faced by every living being. Here are the basics on what causes climate change, how it’s affecting the planet, and what we can do about it.

What is climate change?

The term climate refers to the general weather conditions of a place over many years. In the United States, for example, Maine’s climate is cold and snowy in winter while South Florida’s is tropical year-round. Climate change is a significant variation of average weather conditions—say, conditions becoming warmer, wetter, or drier—over several decades or more. It’s that longer-term trend that differentiates climate change from natural weather variability. And while “climate change” and “global warming” are often used interchangeably, global warming—the recent rise in the global average temperature near the earth’s surface—is just one aspect of climate change.

How is climate change measured over time?

Earth-orbiting satellites, remote meteorological stations, and ocean buoys are used to monitor present-day weather and climate, but it’s paleoclimatology data from natural sources like ice cores, tree rings, corals, and ocean and lake sediments that have enabled scientists to extend the earth’s climatic records back millions of years. These records provide a comprehensive look at the long-term changes in the earth’s atmosphere, oceans, land surface, and cryosphere (frozen water systems). Scientists then feed this data into sophisticated climate models that predict future climate trends—with impressive accuracy.

What causes climate change?

The mechanics of the earth’s climate system are simple. When energy from the sun is reflected off the earth and back into space (mostly by clouds and ice), or when the earth’s atmosphere releases energy, the planet cools. When the earth absorbs the sun’s energy, or when atmospheric gases prevent heat released by the earth from radiating into space (the greenhouse effect), the planet warms. A variety of factors, both natural and human, can influence the earth’s climate system.

Natural causes of climate change

As we all know, the earth has gone through warm and cool phases in the past, and long before humans were around. Forces that contribute to climate change include the sun’s intensity, volcanic eruptions, and changes in naturally occurring greenhouse gas concentrations. But records indicate that today’s climatic warming—particularly the warming since the mid-20th century—is occurring much faster than ever before and can’t be explained by natural causes alone. According to NASA, “These natural causes are still in play today, but their influence is too small or they occur too slowly to explain the rapid warming seen in recent decades.”

Anthropogenic causes of climate change

Humans—more specifically, the greenhouse gas (GHG) emissions we generate—are the leading cause of the earth’s rapidly changing climate. Greenhouse gases play an important role in keeping the planet warm enough to inhabit. But the amount of these gases in our atmosphere has skyrocketed in recent decades. According to the Intergovernmental Panel on Climate Change (IPCC), concentrations of carbon dioxide, methane, and nitrous oxides “have increased to levels unprecedented in at least the last 800,000 years.” Indeed, the atmosphere’s share of carbon dioxide—the planet’s chief climate change contributor—has risen by 40 percent since preindustrial times.

The burning of fossil fuels like coal, oil, and gas for electricity, heat, and transportation is the primary source of human-generated emissions. A second major source is deforestation, which releases sequestered carbon into the air. It’s estimated that logging, clear-cutting, fires, and other forms of forest degradation contribute up to 20 percent of global carbon emissions. Other human activities that generate air pollution include fertilizer use (a primary source of nitrous oxide emissions), livestock production (cattle, buffalo, sheep, and goats are major methane emitters), and certain industrial processes that release fluorinated gases. Activities like agriculture and road construction can change the reflectivity of the earth’s surface, leading to local warming or cooling, too.

Though our planet’s forests and oceans absorb greenhouse gases from the atmosphere through photosynthesis and other processes, these natural carbon sinks can’t keep up with our rising emissions. The resulting buildup of greenhouse gases is causing alarmingly fast warming worldwide. It’s estimated that the earth’s average temperature rose by about 1 degree Fahrenheit during the 20th century. If that doesn’t sound like much, consider this: When the last ice age ended and the northeastern United States was covered by more than 3,000 feet of ice, average temperatures were just 5 to 9 degrees cooler than they are now.

The effects of global climate change

According to the World Economic Forum’s 2016 Global Risks Report, the failure to mitigate and adapt to climate change will be “the most impactful risk” facing communities worldwide in the coming decade—ahead even of weapons of mass destruction and water crises. Blame its cascading effects: As climate change transforms global ecosystems, it affects everything from the places we live to the water we drink to the air we breathe.

Extreme weather

As the earth’s atmosphere heats up, it collects, retains, and drops more water, changing weather patterns and making wet areas wetter and dry areas drier. Higher temperatures worsen and increase the frequency of many types of disasters, including storms, floods, heat waves, and droughts. These events can have devastating and costly consequences, jeopardizing access to clean drinking water, fueling out-of-control wildfires, damaging property, creating hazardous-material spills, polluting the air, and leading to loss of life.

Dirty air

Air pollution and climate change are inextricably linked, with one exacerbating the other. When the earth’s temperatures rise, not only does our air gets dirtier—with smog and soot levels going up—but there are also more allergenic air pollutants such as circulating mold (thanks to damp conditions from extreme weather and more floods) and pollen (due to longer, stronger pollen seasons).

Health risks

U.S. Air Force/Master Sgt. Brian Ferguson

According to the World Health Organization, “climate change is expected to cause approximately 250,000 additional deaths per year” between 2030 and 2050. As global temperatures rise, so do the number of fatalities and illnesses from heat stress, heatstroke, and cardiovascular and kidney disease. As air pollution worsens, so does respiratory health—particularly for the 300 million people living with asthma worldwide there’s more airborne pollen and mold to torment hay fever and allergy sufferers, too. Extreme weather events, such as severe storms and flooding, can lead to injury, drinking water contamination, and storm damage that may compromise basic infrastructure or lead to community displacement. Indeed, historical models suggest the likelihood of being displaced by a disaster is now 60 percent higher than it was four decades ago—and the largest increases in displacement are driven by weather- and climate-related events. (It’s worth noting that displacement comes with its own health threats, such as increases in urban crowding, trauma, social unrest, lack of clean water, and transmission of infectious diseases.) A warmer, wetter world is also a boon for insect-borne diseases such as dengue fever, West Nile virus, and Lyme disease.

Rising seas

The Arctic is heating twice as fast as any other place on the planet. As its ice sheets melt into the seas, our oceans are on track to rise one to four feet higher by 2100, threatening coastal ecosystems and low-lying areas. Island nations face particular risk, as do some of the world’s largest cities, including New York, Miami, Mumbai, and Sydney.

Warmer, more acidic oceans

The earth’s oceans absorb between one-quarter and one-third of our fossil fuel emissions and are now 30 percent more acidic than they were in preindustrial times. This acidification poses a serious threat to underwater life, particularly creatures with calcified shells or skeletons like oysters, clams, and coral. It can have a devastating impact on shellfisheries, as well as the fish, birds, and mammals that depend on shellfish for sustenance. Rising ocean temperatures are also altering the range and population of underwater species and contributing to coral bleaching events capable of killing entire reefs—ecosystems that support more than 25 percent of all marine life.

Imperiled ecosystems

Climate change is increasing pressure on wildlife to adapt to changing habitats—and fast. Many species are seeking out cooler climates and higher altitudes, altering seasonal behaviors, and adjusting traditional migration patterns. These shifts can fundamentally transform entire ecosystems and the intricate webs of life that depend on them. As a result, according to a 2014 IPCC climate change report, many species now face “increased extinction risk due to climate change.” And one 2015 study showed that mammals, fish, birds, reptiles, and other vertebrate species are disappearing 114 times faster than they should be, a phenomenon that has been linked to climate change, pollution, and deforestation—all interconnected threats. On the flip side, milder winters and longer summers have enabled some species to thrive, including tree-killing insects that are endangering entire forests.

Climate change facts

Despite what climate deniers and fossil fuel lackeys claim—for instance, that the science on global warming is “far from settled”—there’s nothing to debate climate change is a reality. In its most recent report, the IPCC—the foremost international scientific body for the assessment of climate change—states, “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.” Our last decade—2000 to 2009—was hotter than any other decade in at least the past 1,300 years. Analyses indicate that 2016 was the hottest year on record. The previous record year was 2015. Before that, 2014.

The responsibility to reverse this worrying trend lies with us. At least 97 percent of actively publishing climate scientists endorse the consensus position that humans are the lead drivers of climate change. As the IPCC states with its highest degree of confidence, “It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in GHG concentrations and other anthropogenic forcings together.”

Climate change solutions

We can mitigate global climate change and help stem its detrimental impacts, but doing so will require tackling its root cause: pollution from burning fossil fuels.

Paris climate agreement

At the 2015 Paris Climate Change Conference, nearly every nation on earth committed to actions aimed at shifting away from dirty fossil fuels and toward cleaner, smarter energy options in order to limit global temperature rise this century to 2 degrees Celsius—or 1.5 degrees Celsius, if possible.

For its part, the United States—the second-largest contributor to global emissions, after China—pledged to cut its output by 26 percent to 28 percent (relative to 2005 levels) by 2025. Making good on that pledge, however, will require the country to fully implement the Clean Power Plan, which establishes the first national limits on carbon pollution from power plants. We must also move forward with the Obama administration’s Climate Action Plan, which includes steps to promote renewable energy sources, increase fuel economy standards, prioritize energy efficiency, and reduce emissions of greenhouse gases beyond carbon, such as methane.

Fast-forward to today, and President Trump has threatened to abandon the Paris climate agreement and to eliminate “harmful and unnecessary policies such as the Climate Action Plan.” Indeed, his America First Energy Plan not only promises to shackle the United States to climate-polluting fossil fuels but also ignores the ongoing clean energy revolution, which is creating millions of jobs and saving billions of dollars through investments in solar, wind, and other renewable energy resources.

Pulling out of the Paris climate agreement and reneging on our climate commitments will scuttle the United States’ global lead on climate change and put our environment, prosperity, and national security at risk. It will also fly in the face of the 71 percent of Americans, including 57 percent of Republicans, who support U.S. participation in the accord. “Americans know that if we retreat from the Paris agreement, we’re retreating from our fundamental obligation to leave our children a livable planet,” says NRDC President Rhea Suh. We must fight to keep a seat at the table, and to ensure the Trump administration doesn’t water down the climate commitments to which we agreed.

Climate action at home

Tackling global climate change is a Herculean task, one that depends on international consensus and the efforts of communities, companies, and individuals alike. To that end, California, Illinois, Iowa, and other states are championing clean energy industries, such as solar and wind cities like Philadelphia and New York are taking action to mitigate climate change and bolster climate resilience and in November 2016, hundreds of American companies voiced their support for low-emissions policies and the Paris climate agreement. There are myriad ways that you can help, too. Picking up the phone to call Congress about environmental policies that matter, supporting renewable energy projects, and prioritizing fuel and energy efficiency will not only curb individual carbon emissions but bolster clean alternatives to dirty fossil fuels. We must all step up—and now.

9.5: Anthropogenic Causes of Climate Change - Biology

Yes, by increasing the abundance of greenhouse gases in the atmosphere, human activities are amplifying Earth’s natural greenhouse effect. Virtually all climate scientists agree that this increase in heat-trapping gases is the main reason for the 1.8°F (1.0°C) rise in global average temperature since the late nineteenth century. Carbon dioxide, methane, nitrous oxide, ozone, and various chlorofluorocarbons are all human-emitted heat-trapping gases. Among these, carbon dioxide is of greatest concern to scientists because it exerts a larger overall warming influence than the other gases combined.

Steam billows from the Intermountain Power Plant in Delta, Utah. This coal-fired plant is operated by the Los Angeles Department of Water and Power. Photo CC license by Matt Hintsa.

At present, humans are putting an estimated 9.5 billion metric tons of carbon into the atmosphere each year by burning fossil fuels, and another 1.5 billion through deforestation and other land cover changes. Of this human-produced carbon, forests and other vegetation absorb around 3.2 billion metric tons per year, while the ocean absorbs about 2.5 billion metric tons per year. A net 5 billion metric tons of human-produced carbon remain in the atmosphere each year, raising the global average carbon dioxide concentrations by about 2.3 parts per million per year. Since 1750, humans have increased the abundance of carbon dioxide in the atmosphere by nearly 50 percent. Learn more.

What Causes Climate Change?

Despite a vocal minority of climate deniers, there is no reasonable doubt that the climate is changing, and that the change is the result of human activity. But climate science is complicated, and few adults learned about it in school. If you do not understand climate change as well as you’d like, let this be your introduction to a basic understanding of climate science. Welcome to Climate Change 101.

What Is Climate Change?

As explained in the first article in this series, climate change is the environmental crisis created by greenhouse gases released into the atmosphere by human industrial activity. The concentration of carbon dioxide (CO2) in the atmosphere has increased from about 280 parts per million in the 1800s to more than 415 parts per million today and is still increasing rapidly.

Climate change is an environmental crisis because humans evolved and societies grew during a long cool era in Earth’s history that has ended because our industrial emissions drove average global temperatures higher. Humans, not nature, must change their behavior to restore the atmosphere to the state in which we developed as a species. Our survival is at risk.

This increased concentration has intensified the natural greenhouse effect of the earth’s atmosphere. It has raised the global average surface temperature by 3.6 degrees Fahrenheit (2 degrees Celsius) and is causing a cascade of complex shifts to climate patterns. These disruptions result in more frequent and more extreme weather events, redistribution and destruction of wildlife populations, and many other harmful changes.

Greenhouse Gases

There are many greenhouse gases (GHGs), including methane, nitrous oxide, fluorinated gases, carbon dioxide, and even water vapor. Except for the fluorinated gases (chlorofluorocarbons and hydrofluorocarbons), which are human-made, any of these gases can occur naturally or be generated by human activity.

Each gas has a different ability to trap heat (known as its global warming potential) and a different lifetime in the atmosphere. Among the GHGs, water vapor is the most common by volume, and the fluorinated gases are the most potent, with global warming potentials measured in thousands. However, carbon dioxide is the most significant to climate change because we are adding so much of it to the atmosphere. And once released, it remains in the atmosphere for a very long time – up to 1,000 years.

Image by JuergenPM from Pixabay

Natural Causes of Climate Variability

Baseline quantities of carbon dioxide are generated through natural processes like ocean-atmosphere exchange soil, plant, and animal respiration and decomposition. The atmosphere, like all natural systems, is variable. The concentration of greenhouse gases in the atmosphere naturally fluctuates.

Using ice core samples, scientists can measure historical concentrations of CO2 in the air. During the last 400,000 years, the natural variation in atmospheric CO2 levels was between 200-280 parts per million. Regularly recurring factors such as the seasons, oceanic cycles, and the solar Schwabe cycle create some of the variation. Irregular occurrences like volcanic eruptions and large forest fires can contribute to variations as well.

But all of these sources combined do not account for the changes that have been documented in the last century.

Anthropogenic Greenhouse Gases

Climate change is anthropogenic. Anthropogenic is a big word that simply means “caused by people.” Humans have increased atmospheric carbon dioxide levels by 45 percent since the beginning of the Industrial Age. Half of that increase has occurred since 1980, and one-quarter since 2000. Methane concentrations have increased 2.5 times in the same time period, with most of the increase occurring since 1980.

Natural cycles and rare natural events combined do not result in such high numbers. But these numbers are consistent with post-industrial emissions levels. In 1950, atmospheric CO2 levels reached their highest point in 800,000 years, and they have been increasing exponentially since.

This graph provides evidence that atmospheric CO2 has increased dramatically since the Industrial Age. Image:

But this circumstantial evidence is not the only reason to identify anthropogenic causes for climate change. According to NASA, carbon produced by burning fossil fuels has a different ratio of heavy-to-light carbon atoms, so it leaves a distinct “fingerprint” that instruments can measure. The measured decline in carbon-13 isotopes in the atmosphere indicates that the increased carbon dioxide levels are the result of burning fossil fuels.

Global Causes of Climate Change

Globally, the top sources of greenhouse gas emissions are:

  • Electricity and heat production (25%)
  • Agriculture, forestry, and other land uses (24%)
  • Industry (21%)

More than half (53 percent) of global GHG emissions are generated in Asia, where China alone accounts for more than one-quarter of the world’s total. However, Asia houses 60 percent of the world’s population, and much of China’s industrial output is for North American consumption. This puts per capita emissions in Asia slightly below the world average.

American Causes of Climate Change

North Americans, on the other hand, have a very high per capita GHG production. The United States, with only 4.3 percent of the world’s population, generates 15 percent of global greenhouse gases. Furthermore, while Asia has only recently become an important contributor to climate change the U.S. has emitted more total CO2 than any other country. The United States has released about 400 billion tons total, making it responsible for 25 percent of historical emissions.

Fossil fuel use in the U.S. also follows a slightly different pattern from the rest of the world. Using 2018 data, the EPA estimates total U.S. GHG emissions by economic sector. Their estimates indicate that transportation generates 28 percent of the GHGs in the U.S. Electricity follows as a close second at 27 percent. Greenhouse gas emissions from transportation overwhelmingly – 90 percent – come from burning gasoline and diesel fuels.

Fortunately, transportation is one area where most individuals have a level of control and can take measures to reduce their impact.

Most greenhouse gas emissions from generating electricity – about 63 percent – come from power plants that burn coal and natural gas. Individuals usually have less control over their electricity sources. But there are some actions individuals can take to both green their energy supply and reduce their electricity use.

The third article in this series deals with the consequences of climate change.

Increases in greenhouse gases due to human activities

Carbon dioxide is being added to the atmosphere faster than it can be removed by other parts of the carbon cycle.

Since the Industrial Revolution there has been a large increase in human activities such as fossil fuel burning, land clearing and agriculture, which affect the release and uptake of carbon dioxide.

According to the most recent Emissions Overview, carbon dioxide and other greenhouse gases are produced in NSW by the following activities or sources:

  • stationary energy sources, such as coal-fired power stations (47 per cent)
  • transport (18 per cent)
  • coal mines (12 per cent)
  • agriculture (11 per cent)
  • land use (7 per cent)
  • land change (3 per cent)
  • waste (2 per cent).

Carbon dioxide released into the atmosphere from burning fossil fuels carries a different chemical fingerprint from that released by natural sources such as respiration and volcanoes. This makes it possible to identify the contribution of human activity to greenhouse gas production.

Data collected by CSIRO show that the concentration of carbon dioxide in our atmosphere in 2018 was approximately 404 parts per million. The level of carbon dioxide in the Earth&rsquos atmosphere is now higher than at any time over the past 800,000&mdashand possibly 20 million&mdashyears.

Global atmospheric concentrations of the other greenhouse gases (methane and nitrous oxide) also now exceed pre-industrial values. For the latest measurements, visit CSIRO&rsquos Cape Grim Greenhouse Gas Data.

Causes for rising emissions

  • Burning coal, oil and gas produces carbon dioxide and nitrous oxide.
  • Cutting down forests (deforestation). Trees help to regulate the climate by absorbing CO2 from the atmosphere. When they are cut down, that beneficial effect is lost and the carbon stored in the trees is released into the atmosphere, adding to the greenhouse effect.
  • Increasing livestock farming. Cows and sheep produce large amounts of methane when they digest their food.
  • Fertilisers containing nitrogen produce nitrous oxide emissions.
  • Fluorinated gases are emitted from equipment and products that use these gases. Such emissions have a very strong warming effect, up to 23 000 times greater than CO2.

Coral reefs and climate change

Anthropogenic greenhouse gas emissions have caused an increase in global surface temperature of approximately 1°C since pre-industrial times. This has led to unprecedented mass coral bleaching events which – combined with growing local pressures – have made coral reefs one of the most threatened ecosystems on Earth.

When conditions such as the temperature change, corals expel the symbiotic algae living in their tissues, responsible for their colour. A spike of 1–2°C in ocean temperatures sustained over several weeks can lead to bleaching, turning corals white. If corals are bleached for prolonged periods, they eventually die. Coral bleaching events often lead to the death of large amounts of corals.

Reefs around the world have suffered from mass bleaching events for three consecutive years. Iconic reefs such as the Great Barrier Reef in Australia and the Northwestern Hawaiian Islands in the United States have all experienced their worst bleaching on record with devastating effects. The bleaching of the Great Barrier Reef in 2016 and 2017, for instance, killed around 50% of its corals.

Corals cannot survive the frequency of current bleaching events from global temperature rise. If temperatures continue to rise, bleaching events will increase in intensity and frequency. Scientists estimate that even those events that occur twice per decade can threaten corals’ survival. The first global scientific assessment of climate change impacts on World Heritage coral reefs, published in 2017 by UNESCO, predicts that the coral reefs in all 29 reef-containing World Heritage sites would cease to exist as functioning coral reef ecosystems by the end of this century if humans continue to emit greenhouse gases under a business-as-usual scenario.

Why is it important ?

Coral reefs harbour the highest biodiversity of any ecosystem globally. Despite covering less than 0.1% of the ocean floor, reefs host more than one quarter of all marine fish species, in addition to many other marine animals. Additionally, reefs provide a wide variety of ecosystem services such as subsistence food, protection from flooding and sustaining the fishing and tourism industries. Their disappearance will therefore have economic, social and health consequences.

Coral reefs are estimated to directly support over 500 million people worldwide, who rely on them for daily subsistence, mostly in poor countries. A 2014 assessment published in the journal Global Environmental Change estimated the social, cultural and economic value of coral reefs at US$1 trillion. A 2015 study by WWF projects that the climate-related loss of reef ecosystem services will cost US$500 billion per year or more by 2100.

Coral reefs are also key indicators of global ecosystem health. They serve as an early warning sign of what may happen to other less sensitive systems, such as river deltas, if climate change is not urgently addressed. Once the tipping point for the survival of coral reefs is passed, the deterioration of other systems may cascade more quickly and irreversibly.

What can be done?

Limiting global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C, in line with the Paris Agreement on climate change, provides the only chance for the survival of coral reefs globally. If the agreement is fully implemented, we will likely see a decrease in atmospheric carbon concentrations. This will improve conditions for the survival of reefs, and enable other measures to rescue reefs to be successful. Other measures alone, such as addressing local pollution and destructive fishing practices, cannot save coral reefs without stabilised greenhouse gas emissions.

Reinforcing commitments to the Paris Agreement must be mirrored in all other global agreements such as the Sustainable Development Goals. SDG 13, for instance, calls for urgent action to combat climate change and its impacts.

There also needs to be a transformation of mainstream economic systems and a move towards circular economic practices. These are highlighted in SDG 8 (inclusive and sustainable economic growth) and SDG 12 (sustainable consumption and production patterns). Economic systems need to rapidly move to the low greenhouse gas emission scenario to enable global temperature decrease.

A move away from current economic thinking should include the benefits provided by coral reefs, which are currently not taken into account in mainstream business and finance. Therefore, sustaining and restoring coral reefs should be treated as an asset, and long-term investments should be made for their preservation.

Investments should also include support for research at the frontiers of biology, such as genetic selection of heat-resistant corals that can withstand rising global temperatures.

Natural Climate Change

Earth’s climate has always been driven by the amount of incoming and outgoing energy. Without the influence of humans, the Earth has natural cycles that drive the climate. The major factors contributing to Earth’s natural climate change are determined by the [Axial tilt|Earth's orbit around the sun], the output of energy from our sun, the ocean’s natural cooling and warming cycles and the constant variability in volcanic activity. Another factor to consider are the glacial advances and retreats that occur throughout Earth’s history. In the last 650,000 years, there have been around seven ice ages, the most recent ending around 12,000 years ago. ΐ] Since then, the Earth has experienced a glacial advance known as the little ice age, which occurred from the 16th century through to the 19th century. However, earth is still in the natural warming process from this glacial advance and many climate change deniers erroneously claim that this is the cause for the current dramatic climate changes. Although natural climate factors have some effect on the current global warming, they are not as drowned out by the human induced factors. Ώ]

9.5: Anthropogenic Causes of Climate Change - Biology

Join Dr. Ken N. Paige, Professor in the Department of Evolution, Ecology, and Behavior at the University of Illinois, on Monday, April 12 @ Noon CST via Zoom to learn about climate change and biodiversity.

In this presentation, Dr. Ken Paige will discuss the causes of anthropogenic climate change and biological responses that have been widely documented across taxa and regions. Documented responses include population decay and local extirpation, geographic range shifts, altered phenologies, and biome regime shifts. He will also discuss whether species are maintaining a good match between phenotype and environment, i.e. whether observed trait changes are adaptive.

Dr. Paige will also touch upon the differences and consequent similarities between invasive and native species in light of climate change. Unlike the introduction of non-native species, which tends to be idiosyncratic and usually depends on human-mediated transport, climate-driven redistribution is ubiquitous, follows repeated patterns, and is poised to influence a greater proportion of Earth’s biota.

A little about Dr. Ken N. Paige. Dr. Paige holds BS and MS degrees in wildlife management/biology from Arkansas State University and a Ph.D. in ecology/evolutionary biology from Northern Arizona University. Following his Ph.D., he conducted postdoctoral work at the University of Utah in molecular genetics. He joined the Institute for Environmental Studies and the Department of Ecology, Ethology, and Evolution at the University of Illinois, Urbana-Champaign in 1988. He is currently a Professor in the Department of Evolution, Ecology, and Behavior at the U of I where he served 12 years as the Head of the Department. He works in the fields of plant-animal interactions and conservation biology using a combination of field studies and molecular genetic approaches. Web page:

This program is brought to you by our University of Illinois Extension Master Naturalist volunteers. Our East Central Illinois Master Naturalist mission is to develop an expanding corps of well-educated volunteers to provide service and support for partnering organizations in the conservation, restoration, management, and interpretation of natural resources and natural areas in East Central Illinois. Sessions will be recorded and available on our YouTube Channel. Find more at

This event is free and open to the public. If you need reasonable accommodations, please call Randy at 217-333-7672

Climate Change Introduction, Causes, Effects & Efforts


  • As per United Nations Framework Convention on਌limate Change(UNFCCC), climate change means a਌hange in the਌limate of the earth that is attributed directly or indirectly to human activity which alters the composition of our atmosphere.
  • The variation and periodical shifts in weather conditions over space and time, resulting in the change in climate may also be defined as Climate Change. Ex – Change of climate from warm and moist to warm and dry.
  • It is a change in the local, regional or global environment caused due to rise in the global temperature and human activities.
  • The rate of climate change relies on the pace of the causal factor.
  • Climate may change gradually or rapidly, partly or drastically, short term or long term, over Local, regional, or global scale, depending on the pace of causal factors.
  • The disastrous effect of climate change may be understood by the fact that during the Jurassic Period, climate change leads to the mass extinction of Dinosaurs due to the rapid onset of Cold Climate.

Areas of concern

  • According to a research study by the Intergovernmental Panel on Climate Change (IPCC), human activities have led to an increase in global temperature of about 1 ° C (0.8 ° C to 1.2 ° C) above pre-industrial levels.
  • The global temperature may rise by 1.5 ° C between 2030 and 2052 if it continues to rise at the present rate.
  • The atmospheric concentrations of the primary greenhouse gas (CO2) have increased to 410 parts per million (ppm) from about 280 ppm from pre-industrial times.
  • As per an estimate of WHO, climate change may be the prime reason for the death of around 250,000 people every year due to increasing pollution-related problems.
  • The poorest people will be the most affected section from climate change.

Evidence of Climate Change

Following are the evidence which proves that climate change is a reality and needs to be taken into account for future policies and action:-

  • A rise in the Global Temperature
  • A decrease in the snow cover on Glaciers
  • A reduction in Arctic Sea Ice Cover
  • Warming of Ocean Waters
  • The rising sea level of Ocean
  • Increase in the event of forest fires around the world
  • Ocean acidification resulting in the death of marine plants and animals
  • Extreme weather events on regular intervals. Like – excessive precipitation, floods, earthquakes, tsunamis, high winds, hail, thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones etc.

Causes of climate change

There are many reasons for climate change.

They can be divided into natural causes and anthropogenic causes:-

Natural causes of climate change

The important natural factors causing climate change are appended below-

  • Continental Drift - It changes the physical features of the water bodies and landmass, which further alters the flow of ocean currents and winds.
  • Change in the variation of Earth’s Orbit - It produces ‘Milankovitch cycles’ which have an enormous impact on climate and have a notable correlation to glacial and interglacial periods.
  • Pollution due to Volcanic Activities - During Volcano eruption, the outburst of gases and dust particles abrupt the incoming rays of the Sun. Also, Sulphur dioxide produced from volcanoes combines with the water to form tiny droplets of Sulphuric acid, which can stay in the environment for several years.
  • Plate Tectonics - The shifting of the continents also affects patterns of ocean currents as it changes the geometry of the oceans.
  • Change in the pattern of Ocean Currents – Horizontal winds result in the displacement of the water against the sea surface. If it changes, it may change the climatic condition.

Anthropogenic causes of climate change

The various manmade factors affecting climate change are appended below-

  • Excessive emission of Greenhouse Gases – It causes pollution in the atmosphere which results in the changes in the patterns of climate.
  • Change in the composition of Atmospheric Aerosols - Aerosols cause scattering and absorbing of the solar and infrared radiation. Also, they can change the microphysical and chemical properties of clouds.
  • Deforestation – Due to Cutting down of trees and forests, the amount of sunlight reflected from the ground back into space is changing, which is changing the climate pattern. Also, forest acts as a carbon sink, if it decreases due to deforestation, it will disturb the balance in the atmospheric composition.
  • Excessive exploitation of natural resources – The nature has a tremendous load on its natural resources due to growth in population and increase in the demand.
  • Policy Priority to industrialization than the environment – In a race for industrialization, Governments around the world are formulating policies with a tilt towards more industrialization. Environmental impacts are being ignored.
  • Excessive emission of CO2 – Industrialization & increasing in use of the vehicle is increasing the emission of CO2.

Impacts of climate change

Our planet earth is experiencing some significant changes due to variation in climatic condition. Some significant impacts of climate change are appended below:-

  • Increased risk of extreme weather events
  • Increased risk of forest fires
  • Increased risk of floods
  • Increased risk of Droughts
  • Increased risk of Diseases and illness
  • Increased economic losses caused due to extreme weather events
  • A rise in the sea levels
  • The surge in Global Temperature
  • A threat to the ecosystem and wetlands

India’s effort to counter climate change

National action plan on climate change (NAPCC)

Govt has launched the following programmes to address climate change under NAPCC:-

Watch the video: The Anthropogenic Activities affecting Climate Change. A Level Geography 2021 (July 2022).


  1. Mekhi

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  2. Duzragore

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  3. Kester

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  4. Denzell

    What do you usually do with me?

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