Global climate change refers to variations in the Earth’s climatic conditions stemming from internal and external forces. The Earth’s natural internal variability causes climate to vary over millennia. This internal variability includes factors such as volcanic eruptions and ocean heat redistribution. External forcings such as solar output and orbital variations will impact climate, while ever-increasing anthropogenic forcings like greenhouse gases and aerosols are becoming a serious problem.
- What is global climate change?
- The causes of global climate change
- Natural causes of climate change
- Human external forces of climate change
- Impacts of global climate change
- Climate change impacts on global food security
- Agriculture on land
- Coastal agriculture
- Climate change prevention
- Difference between climate change and global warming
What is Global Climate Change?
Global climate change refers to the long-term shifts in the Earth's climate patterns, including changes in temperature, precipitation, wind patterns, and other measures of climate over decades or longer periods.
Climate change affects more than just the climate though. Changes in the physical ecosystem will affect the living ecosystem too: plants, animals, insects, etc. will have to adapt to the ongoing changes or find a new habitat to live in.
Climate change can therefore cause a decrease in biodiversity if certain species are not able to adapt well or fast enough to changes. Accelerating climate change through human activities can therefore have important impacts on the ecosystem's equilibrium and biodiversity on the planet by decreasing the time that species have to adapt to changes in their physical environment.
The Causes of Global Climate Change
Global climate change has a variety of causes, often called forcings. These include internal and external forcings. External forcings can be natural or anthropogenic. Climate forcings will ‘force’ climatic conditions in one way or the other, depending on whether the Earth’s system is warming (positive forcing) or getting colder (negative forcing).
Natural Causes of Climate Change
Internal forcings
Natural internal variability encompasses the inherent cyclical mechanisms which contribute to global temperatures that influence the various climatic conditions (precipitation, wind patterns, cloud cover etc.). Here are some examples of internal forcings:
Volcanic activity: eruptions from volcanoes can expel masses of dust and sulphur dioxide into the atmosphere, which form aerosols in the atmosphere, contributing to the cooling of the planet.
Ocean cycles: the redistribution of heat by the various multidecadal cycles of the Pacific and Antarctic ocean results in varying sea surface temperatures at the tropics and the poles between decades, which directly influence the air temperature above them. Important cycles include the El Niño Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), and the Interdecadal Pacific Oscillation (IPO).
Orogeny: orogeny is the process by which tectonic plates shift forming mountain ranges and causing continental uplift on a multi-millennial basis. Orogenic uplift has the ability to influence atmospheric circulation patterns and in turn climate variation.
There was a climate change "hiatus" from 1998-2013 that managed to divide public opinion on the effects of human greenhouse gas (GHG) emissions on climate change. Natural decadal variability between 1998 and 2013, along with the cooling effect of aerosols, counteracted the warming effects of GHG emissions in this period.
An unusually strong El Niño of 1997/98 resulted in a decrease in sea-surface temperatures (SST) of the Pacific Ocean in the following years, caused by the responding El Niño. This was coupled with the simultaneous positive shifting of the Atlantic Multidecadal Oscillation (AMO), which favours the El Niño response via tropical sea basin interactions. The Interdecadal Pacific Oscillation (IPO) was intensified as a result, providing an explanation for the global climate hiatus.
Natural External Forcings
Natural external forcings include variables which are not caused by humans or the planet itself. These include:
Obliquity: variations in the degree of tilt of the Earth influences the solar radiations received at different latitudes. If the angle is increased, equatorial regions will receive more solar radiation, causing warmer temperatures and increased vegetation, and regions nearer the poles will experience less solar radiation, causing colder temperatures and scarce vegetation.
Eccentricity: eccentricity refers to the variations in the Earth’s orbit around the sun. The perihelion is when the Earth is closest to the sun, and depending on which hemisphere is pointing towards the sun at this point, this hemisphere will receive more solar radiation.
Solar cycles: there are approximately 11-year solar cycles exhibited by the sun. Controlled by the sun’s magnetic field, and detectable by the positions of sunspots on its surface, these cycles can prove to be very unpredictable.
Human External Forcings of Climate Change
Anthropogenic greenhouse gases: greenhouse gases such as carbon dioxide, methane, nitrous oxide, and CFCs are released into the atmosphere via human activity such as the burning of fossil fuels, industrial processes and agriculture. These gases will contribute to the greenhouse effect by trapping in reflected solar radiation from the Earth’s surface thus warming the atmosphere.
Fig. 2: the Greenhouse effect, Global Climate Change.
Aerosols: the main source of aerosol emission is from cars and factories. These tiny particles will accumulate in the upper atmosphere and reflect sunlight back into space, cooling the planet in the process. Aerosols are a collection of both particles and air (the surrounding gas).
Particulate matter: the microscopic solid or liquid particles taken separately from the gas mixture that makes up the air they are suspended in. Harmful when reaching our lungs, particulate matter is measured as PM. The most harmful seems to be the particulate matter with a diameter 10 microns (µm) or less. This includes dust, dirt, soot, sulfates and nitrates. They can originate from both natural (volcanic eruptions, dust storms) and anthropogenic sources (crop burning).
Chlorofluorocarbons (CFCs) are a category of chemicals used mainly for refrigeration. They cause harm to the ozone layer once released into the atmosphere, by destroying oxygen bonds and preventing them from forming in the stratospheric gas layer of the Earth. CFCs also absorb infrared radiation, leading to climate change. In fact, they absorb more infrared radiation than most other greenhouse gases.
Impacts of Global Climate Change
Rising atmospheric temperatures resulting from natural internal variability, external forcings and anthropogenic emissions have considerable impacts on the different spheres of the Earth. We shall focus on the effects of the warming temperatures we are currently facing:
Natural internal variability is the continual process by which the Earth’s climate varies because of the way natural processes redistribute energy around the planet, causing chain reactions of heat transfer and loss from the different spheres.
Changes in Oceans
Increases in global temperatures and atmospheric greenhouse gases, especially carbon dioxide, are threatening the oceans in a variety of ways:
Rising sea levels: increasing temperatures are causing seawater to expand, especially around the equator, resulting in sea levels rising (since 1880 sea levels have risen 8-9 inches). Melting ice at the poles will also cause sea levels to rise.
Ocean acidification: the exponential increase in atmospheric carbon dioxide content has resulted in masses of CO2 being absorbed into the oceans. Dissolved CO2 forms carbonic acid, making the ocean more acidic. This increased acidity negatively impacts creatures who require carbonate-based shells and exoskeletons, as well as species which are sensitive to acidity. Increases in carbon dioxide levels simultaneously reduce oxygen levels in the ocean.
Changes in ocean currents: ocean currents are affected by melting ice. Melting decreases surface salinity, increases surface temperatures, and causes heavier saline water to sink. This distorts the differences in temperature and density which allow upwelling currents to function. This adversely affects the Global Conveyor Belt, which is essential in distributing nutrients and maintaining the climates of many regions. (Fig. 1: The Global Conveyor Belt, Global Climate Change, StudySmarter)
The Global Conveyor Belt is a worldwide network of upwelling, downwelling, surface and deepwater currents which help distribute nutrients throughout the ocean and carry warm water from the tropics to the poles. Upwelling occurs when deep, cold water rises to the surface, while downwelling occurs when surface water sinks back down to the depths.
Decreased oxygen levels in the ocean, also known as ocean deoxygenation, affect the marine organisms' survival through the direct threat of suffocation. The effect of low dissolved oxygen levels on plankton for example is that it slows their growth and reproduction rates. Marine animals may also change behaviour and spatial distribution to chase higher-oxygen water currents, meaning that local economies that depend on fishing can be affected.
Changes in the Cryosphere
Increasing temperatures are having damaging effects on the cryosphere as well:
Reduced snow cover: warmer temperatures are causing snow to melt and the habitats of many polar animals to be taken away. The melting of ice in coastal regions is detrimental to many coastal communities that have to migrate inland. Reduced albedo (reflection) due to the loss of white snow covering the surface also means more radiation reaches and is absorbed by the (darker in colour) ground.
Changes in precipitation patterns: changes in frequency and severity of precipitation patterns puts human inhabitants in danger as well as many ecosystems because of the unpredictability of the weather in colder regions.
Loss of fish stocks: decreased productivity in oceans surrounding the poles resulting from changes in ocean currents and ocean acidification has led to a reduction in fish populations. This will impact the functionality of ecosystems as well as human populations.
The cryosphere refers to the portion of the Earth's surface where water is in a solid state, including ice and snow.
Changes in the Atmosphere
Human-induced climate change will affect the composition of the atmosphere too:
Greenhouse gases: anthropogenic greenhouse gas emissions, which have escalated in the last 150 years, will add to the greenhouse effect (the trapping of the solar radiation reflected from the Earth’s surface). Carbon dioxide released by humans contributes to 60% of anthropogenic GHG emissions.
Water vapour: a greater greenhouse effect will result in a warmer planet, consequently leading to increased evaporation of the oceans, and reduced likelihood of atmospheric water vapour condensing and forming precipitation. Water vapour itself is a greenhouse gas and has the largest influence on the greenhouse effect.
Cloud cover: increasing temperatures will increase cloud cover (water vapour) in the Earth’s atmosphere. Low thick clouds will reflect sunlight back into space, providing one of the Earth’s feedback systems to climate change.
Aerosols: aerosols released by human activity and volcanic eruptions will accumulate at the top of the atmosphere and in clouds, contributing to the reflection of the sun's radiation, cooling the planet in the process.
An aerosol is a suspension of a tiny particle, often called a particulate, in the air.
Climate Change Impacts on Global Food Security
Variations in temperatures, precipitation patterns, severe weather, and atmospheric greenhouse gases like carbon dioxide will all have impacts on the biosphere and consequently agricultural communities.
Agriculture on Land
The plants that agricultural systems depend on such as crops and trees need fertile soils, water and specific solar radiation thresholds. Too much or too little of any of these elements may cause various species to change behaviour. Climate change has the potential to change rainfall patterns, raise global temperatures, and induce drier soil conditions.
Livestock production
Rising temperatures directly affect livestock production as they result in more energy being lost to sweating and movement.
The increased frequency of heat waves will put animals under stress..
Warmer temperatures have the potential to reduce the fertility of livestock.
Disease-spreading bacteria will thrive in warmer temperatures and will spread easier between livestock.
Droughts will limit the amount of grass for grazing animals.
Agrochemicals will become more prevalent when agricultural communities have to deal with climate change, which will mean the livestock will have weakened immune systems.
Crop production
Increasing temperatures will increase the rates of photosynthetic and biochemical processes up to a certain point, past which yields will worsen.
The warming of certain regions may cause farmers to change which crops they grow, eradicating many crops which require milder temperatures in the process.
Invasive weeds and pests can potentially work better under warmer conditions, meaning that more agrochemicals will need to be used, which may come at the expense of crop health and yield.
Warmer temperatures will cause decomposers to convert detritus to nutrients faster, improving soil health, but releasing more carbon dioxide.
Droughts, floods and extreme temperatures will all cause stress on crop populations and the unpredictability of these weather patterns will make it more difficult for farmers to be ready for them.
Disease-spreading bacteria will spread faster in warmer, wetter environments.
Increased carbon dioxide will mean faster photosynthesis but often results in less healthy plants.
Coastal Agriculture
Rising ocean temperatures may cause certain marine species to migrate north to colder waters, which can reduce the catch made by fishermen.
Disease spreads much easier in warmer waters.
Seasonal variability stemming from global warming will affect reproduction timing in fish communities, meaning fishermen will be unaware when the best time to fish will be.
Ocean acidification affects marine species which build up calcareous shells and exoskeletons, consequently impacting the ecosystems they uphold.
Water pollution will lead to the reduction of many fish populations.
Climate Change Prevention
Climate change prevention includes all actions and strategies aimed at reducing the rate of climate change we are currently at. Climate change prevention is not achievable at the individual level but requires a joint effort from the whole of society, governments and industries. Some examples of strategies to reduce or slow down climate change are:
- Reduce energy use: at a personal level, we can reduce our energy use by turning off lights when we're not using them, using energy-efficient appliances, and insulating our homes to reduce heating and cooling needs. This not only reduces our carbon footprint but also saves money on energy bills! However, there are other similar measures that enterprises also need to take. For example, stores could avoid leaving their storefronts illuminated at night, and industries should aim at using the most energy-efficient lighting and manufacturing processes.
- Use clean energy: Switching to clean energy sources such as wind, solar, and hydropower can significantly reduce greenhouse gas emissions. Another example is using an electric car rather than a fossil fuel one. However, changing a perfectly functioning traditional car for an electric car is less climate-friendly than sticking to your old car until it needs renewing! Governments and businesses should also invest in clean energy infrastructure to help accelerate the transition to a low-carbon economy.
- Reduce waste: Reducing waste, reusing and recycling materials can help reduce greenhouse gas emissions by reducing the need to extract and produce new materials, or get rid of the old material. It also reduces the amount of waste that ends up in landfills, where it generates methane, a potent greenhouse gas. There are many DIY projects that can be completed by using recycled materials, glass bottles can be used as vases or water-plant pots, and organic waste can be used as a natural fertiliser for your plants!
- Eat a plant-based diet: Animal agriculture is a significant contributor to greenhouse gas emissions. By reducing meat consumption, or switching to a plant-based diet altogether, we can reduce meat production and its toll on the environment. More research into sustainable agriculture is also an important need to stop climate change.
Nonetheless, the most crucial steps towards stopping or decelerating climate change are only regulatable at the government level. Supporting policies and regulations put in place to protect the environment is crucial, and governments need to constantly evaluate the current state of the planet and react by implementing rules that are effective. Most importantly, those rules need to focus on the main contaminants: industries.
Difference between Climate Change and Global Warming
It is important to remember that global warming is one of the factors of climate change, and refers to the increasing temperature of the Earth’s system. The term climate change alludes to the variations in the Earth’s climatic conditions, which include but are not limited to temperature.
Global Climate Change - Key takeaways
Climate change is the variation in the Earth’s climatic conditions caused by natural internal variability and external forcings.
These climatic conditions include temperature, precipitation, wind patterns and cloud cover.
Climate change negatively impacts oceans, the cryosphere, and the atmosphere. Agricultural communities and ecosystems are heavily affected too.
Human-induced climate change stems from the release of greenhouse gases into the atmosphere, 60% of these being carbon dioxide.
Explanations 
Exams 
Magazine 
