Anthropogenic Climate Change

Anthropogenic Climate Change - SQA Key definitions: 

• Anthropogenic - Any process that is 'human-caused'. 

• Anthropogenic greenhouse gas - Any Greenhouse gas emission caused by human action. 

• Climate change - A large-scale, long-term shift in Earth’s weather patterns or average temperatures.

• Desertification - The process of relatively dry land becoming increasingly arid, losing its bodies of water as well as vegetation and wildlife.

• Enhanced greenhouse effect - The enhancement of the natural greenhouse effect through man-made emissions of greenhouse gases, trapping increasing quantities of heat.

• Global warming - The increase in average global temperature caused by anthropogenic greenhouse gas emissions. 

• Greenhouse gas - A group of gases which 'trap' heat within the atmosphere, increasing the atmospheric temperature. 

• Sea level - The average height of the ocean's surface for all stages of the tide over a long period. 

• Soil stability - The ability of soil to maintain its structure and resist displacement or deformation when subjected to external forces like gravity, water flow, wind or heavy loads.

• Weather - The state of the atmosphere at a specific place and time, which changes by the minute, hour, and day.

Anthropogenic greenhouse gases

Climate Change refers to a large-scale, long-term shift in Earth’s weather patterns or average temperatures. These changes occur naturally over time, but human activity is accelerating this. Evidence for climate change can come from tree ring analysis, ice core samples, and observations of changes in ice cover : 

 A key control of the climate is the amount of 'Greenhouse Gases' that are present, including:-

• Carbon dioxide

• Methane

• Nitrous oxide 

• Water vapour

These gases act 'like a blanket' trapping heat within the Earth's atmosphere : 

As previously discussed, the Earth's natural greenhouse effect has caused the Earth's temperature to be higher than it would otherwise be, allowing life to exist. However, human activity has dramatically increased its effect, a process known as 'Anthropogenic Climate Change'. 

Anthropogenic (from the Greek 'anthropos' (human) and 'genesis' (origin)) climate change is driven by the emission of 'greenhouse gases', which greatly increased in production since the 'Industrial Revolution'. 

In the mid-19th century human emitting large quantities of greenhouse gases into the air through the burning of Fossil Fuels for energy and transportation, have greatly enhanced the natural level of the greenhouse effect. 

The graph below shows how the average global temperature has changed since the 1880's. As can be seen, the average temperature shows a clear trend of increasing since this time : 

The graphs below show how the concentration of atmospheric greenhouse gases has increased since the Industrial Revolution : 

Sources of Anthropogenic Greenhouse Gases

The greenhouse gases that are emitted by human actions come from a wide range of activities, the main five actions being : 

• Burning fossil fuels for heat and electricity.

• Fossil fuel use in transport.

• Agriculture.

• Deforestation.

• Cement manufacture.

Impacts of Global Warming and Climate Change

Climate change is not as simple as everywhere getting warmer; the effects are different for different areas. Some areas will experience increased temperatures, decreases in rainfall or changes in precipitation (for example, snow to rain), while others will get higher levels of rainfall or more extreme changes in seasonal temperatures. 

Other changes that can be seen include:-

• More frequent and intense weather events, such as Hurricanes and Cyclones.

• Changes to major weather systems like Monsoon and El Niño, strengthening in some areas, reducing in others.

• Climate bands are moving further north or south (depending on hemisphere), changing what plants or animals can survive in a particular location. 

• Flooding of low-lying land due to sea-level rise.

• Tropical diseases are spreading further north or south, such as malaria, as the carriers follow the climate bands. 

• The melting of snow, ice & glaciers is causing flooding and more water scarcity for communities downstream.

Anthropogenic Climate Change : Snow loss 

The loss of snow and ice cover due to rising global temperatures has the impact of accelerating climate change. As snow and ice melt, the ground or rock below is uncovered. As the albedo of the underlying surface is much lower (snow = ~ 0.85, rock = ~0.1), much less heat is reflected, causing further warming and therefore further melting. This is known as a 'positive feedback loop'. 

This process is leading to the substantial loss of snow and ice cover at the poles : 

As well as in Glaciers around the World :

This loss of snow and ice cover has impacts on local biodiversity as well as impacts on water supplies for communities downriver of the glaciers : 

Anthropogenic Climate Change : Sea Level Rise

The loss of snow and ice also has an impact on global sea levels. Sea ice, when it melts, does not have an impact on sea levels (due to Archimedes' Principle); however, if snow and ice on land melt, this water flows into the oceans, which will increase sea levels. Of major concern in terms of impact on sea levels are two ice sheets, the Antarctic ice sheet and the Greenland Ice Sheet.  Both have shown substantial loss in ice mass over the last 20 years : 

The Greenland ice sheet is currently the primary driver of sea-level rise from land ice. It is melting faster (3-4 faster than Antarctica) and more consistently than Antarctica because it is more exposed to both warm air and warm ocean currents. 

The loss from the Greenland ice sheet is currently currenly raising the global sea level by ~0.8mm per year, however if the Greenland ice sheet were to melt entirely, the meltwater would increase sea levels globally by ~7.4m. The total sea level rise due to all sources is ~4mm per year, making Greenland's ice sheet loss responsible for nearly a 1/4 of the global sea level rise annually : 

Though rising sea levels are partly due to meltwater from glaciers and ice sheets, the largest contributor is the thermal expansion of seawater as it warms : 

As water temperature increases, the molecules that make up the water will vibrate more, causing the volume of a fixed mass of water to increase, reducing its density :

This means that the even without meltwater entering the oceans, the ocean level would rise with increasing temperature as the water that is already there will occupy a large volume. 

The following diagram shows how the sea level is predicted to rise over the next 60-80 years, depending on Greenhouse gas emission rates : 

Anthropogenic Climate Change : Ocean Currents

Climate change also has an impact on ocean currents. As fresh meltwater enters the ocean, this changes the salinity and temperature of the ocean water in that area, which can disrupt the global ocean conveyor belt : 

The impact of this is currently most notable in the North Atlantic off the coast of Greenland.  

In 'normal' conditions, warm water flows north, gets colder and saltier (due to evaporation), becomes dense, and sinks near Greenland. This sinking pulls more warm water up from the south. As the Greenland Ice Sheet melts, however, a massive 'plug' of freshwater is poured into the North Atlantic. Because freshwater is less dense than saltwater, it refuses to sink, disrupting the ocean current. 

Data has shown that the ocean currents off Greenland have already weakened by about 15% since the mid-20th century. If it collapses, Europe could see a dramatic drop in temperature, even as the rest of the world warms, due to the lack of warm water flowing from the Caribbean (the 'Gulf Stream'). 

Anthropogenic Climate Change : Changes in Weather Patterns

Anthropogenic climate change is causing changes in weather patterns globally. 'Weather' is the state of the atmosphere at a specific place and time, which changes by the minute, hour, and day, whereas 'Climate' is the long-term pattern of weather in a particular area. 

Due to anthropogenic climate change, extreme weather events (significantly more severe, rare, or intense than the 'normal' weather patterns for a specific location) are becoming much more common : 

The impacts are very dependent on location, but globally, there are 4 key impacts on weather patterns due to anthropogenic climate change : 

Anthropogenic Climate Change : Soil Stability 

Climate change can also cause impacts on land in terms of 'Soil Stability'. Soil stability is the ability of soil to maintain its structure and resist displacement or deformation when subjected to external forces like gravity, water flow, wind or heavy loads.  

Climate change affects soil stability in a range of ways : 

Anthropogenic Climate Change : Species Distribution

Due to warming global temperatures, many species are being displaced further North or South, seeking cooler temperatures : 

This has a large impact as not all species are displaced at the same rate, risking the collapse of food webs when food sources are lost . 

For example, the maps below show the mismatch between a Butterfly and its host plants, caused by climate change :

Species are also moving to higher elevations where possible, again seeking cooler temperatures. Unfortunately, this has lead to loss of species at the highest elevations, as they have no where further to go :

Changes in Species Distribution Case Study : The Bobolink

For further data from the National Audubon Society showing the changes in the bird ranges of North America due to climate change (including to temperatures above 1.5°C), please follow this link. 

Anthropogenic Climate Change : Economics 

Climate Change has a global economic cost via agricultural yields, the physical and cognitive performance of workers, demand for energy, disaster management, as well as increasing the incidence of crime, unrest, and conflicts.

The graph below shows how the costs of extreme weather events globally have increased since 1980 :

Minimising the Impacts of Anthropogenic Climate Change

• Individual : In order to minimise the impact of an individual person, there is a need to educate the public on ways that they, as individuals, can make a difference. These include : 

• Recycling/ Purchasing products made from recycled goods

• Car sharing/walking, or using public transport instead of using the car

• Switching off lights or turning off appliances when not using them

• Using energy-efficient appliances and light bulbs

• Installing solar panels in your home

• Local : Local government decision-making influences how an area can contribute to minimising the impacts of their communities. These influences include : 

  • • Changes to waste management 

    • Restoring Peatland or afforestation schemes 

    • Modelling good practice, such as converting council vehicles to electric, for example. 

    • Promoting the use of low-carbon transport, for example, cycling, in the local area.

• National : National governments hold the power to drive the social, economic and environmental agendas within their countries. Some methods of this include : 

  • • Introducing legislation to decarbonise the economy. 

    • Funding projects that promote the green economy 

    • Introducing or increasing taxes on activities that contribute to anthropogenic climate change. 

• International : As anthropogenic climate change is a global issue that defies borders, the international community as a whole is required to make changes as a global society to minimise the impacts of humanity. These include : 

  • • The Intergovernmental Panel on Climate Change (IPCC) brings together all climate research from across the globe in order to provide consensus views of climate change and inform government policies globally. 

    • COP conferences are annual global climate summits organised by the United Nations, where nearly every country on Earth gathers to negotiate how to handle anthropogenic climate change. 

    • Sustainable Development Goals are a set of targets created by the United Nations to focus world efforts on meeting sustainability targets globally. Goal 13 explicitly covers 'Climate Action' with many others indirectly involved in minimising the impact of anthropogenic climate change.