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Writer's pictureTom McAndrew

The Climate is Changing

An article about Climate Change, for students of geography. A one-stop shop for the evidence, the causes and effects.



Takeaways

  • While Earth’s climate has changed throughout its history, the current warming is happening at a rate not seen in the past 10,000 years.

  • According to the Intergovernmental Panel on Climate Change (IPCC), "Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact."

  • Scientific information taken from natural sources (such as ice cores, rocks, and tree rings) and from modern equipment (like satellites and instruments) all show the signs of a changing climate.

  • From global temperature rise to melting ice sheets, the evidence of a warming planet abounds.


Evidence for Climate Change


Climate change is one of the most pressing issues facing our planet today. It refers to long-term changes in global temperatures and weather patterns, primarily due to human activities. This summary outlines key evidence for climate change, supported by statistics and sources.




Rising Global Temperatures


The Earth's average surface temperature has increased by approximately 1.1°C since the late 19th century. This warming trend is largely attributed to human activities, such as burning fossil fuels. According to NASA, the past decade (2011–2020) was the warmest on record, with 2020 tying with 2016 as the hottest year globally.


Melting Ice Caps and Glaciers


Glaciers and polar ice caps are shrinking at an alarming rate. The Arctic sea ice minimum has declined by about 13% per decade since 1979, according to the National Snow and Ice Data Centre. Furthermore, the Greenland and Antarctic ice sheets have lost an average of 427 billion tonnes of ice per year between 2006 and 2015, contributing to rising sea levels.


Snow Cover Decline


Snow cover is decreasing globally, providing further evidence of climate change. According to the National Oceanic and Atmospheric Administration (NOAA), the extent of snow cover in the Northern Hemisphere has decreased by approximately 8% over the past 50 years during spring months. This decline affects ecosystems, water resources, and weather patterns, as snow plays a critical role in reflecting sunlight and regulating temperatures. Reduced snow cover also contributes to a feedback loop, where less sunlight is reflected, causing further warming.




Rising Sea Levels


Sea levels have risen by over 20 centimetres since the late 19th century. The rate of rise has accelerated in recent decades, averaging 3.3 millimetres per year since 1993, as reported by the Intergovernmental Panel on Climate Change (IPCC). This is due to melting ice and the thermal expansion of seawater as it warms.


Changes in Weather Patterns


Climate change has led to more frequent and intense weather events. The UK Met Office highlights that the number of extreme weather events, such as heatwaves, floods, and storms, has significantly increased. For example, the European heatwave of 2022 saw record-breaking temperatures exceeding 40°C in the UK for the first time.


Ocean Warming and Acidification


Oceans absorb about 90% of the excess heat caused by greenhouse gas emissions. As a result, ocean temperatures have risen steadily. Additionally, increased carbon dioxide (CO2) in the atmosphere has led to ocean acidification, with surface water pH levels dropping by 0.1 since the Industrial Revolution. The National Oceanic and Atmospheric Administration (NOAA) warns that this affects marine ecosystems, particularly coral reefs.


Evidence from Wildlife and Vegetation


Changes in climate are impacting ecosystems and biodiversity. Species are shifting their ranges towards cooler areas, and some are facing extinction. For instance, the distribution of butterflies in the UK has moved northwards by 70 kilometres on average since the 1970s, according to the UK Centre for Ecology & Hydrology.


Scientific Consensus


There is overwhelming scientific agreement that climate change is real and driven by human activities. A study published in Environmental Research Letters found that 97% of climate scientists agree that human actions are the primary cause of recent global warming.




Are you convinced yet?


The evidence for climate change is robust and comes from multiple independent sources. Rising temperatures, melting ice, rising sea levels, extreme weather, ocean changes, and impacts on wildlife all point to the urgent need for action. Understanding these trends is essential for addressing the challenges posed by a warming planet.


Causes of Climate Change


Takeaways

  • The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.

  • Five key greenhouse gases are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons, and water vapor.

  • While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.


Climate change, characterised by shifts in global temperatures and weather patterns, is driven by natural processes and human activities. Since the Industrial Revolution in the late 19th century, human influence has significantly accelerated the pace of climate change. This summary explores the causes, focusing on the enhanced greenhouse effect, greenhouse gases, and industrial developments.




The Greenhouse Effect


The greenhouse effect is a natural process essential for life on Earth. Certain gases in the atmosphere, such as carbon dioxide (CO2) and methane (CH4), trap heat from the Sun, keeping the planet warm enough to sustain ecosystems. Without this process, the Earth's average temperature would be about -18°C instead of the current 15°C. However, human activities have amplified this effect, leading to global warming. According to the IPCC’s Sixth Assessment Report (2021), human-induced greenhouse gas emissions are the primary drivers of the enhanced greenhouse effect.


Greenhouse Gases and their Sources from Human Activity


Human activities release significant quantities of greenhouse gases, intensifying the greenhouse effect. Key greenhouse gases include:


1. Carbon Dioxide (CO2): Responsible for about 75% of greenhouse gas emissions. It is released primarily through burning fossil fuels (coal, oil, and natural gas) for energy, transportation, and industry. Deforestation also contributes by reducing the number of trees that absorb CO2 (IPCC, 2021).


2. Methane (CH4): Although less abundant, methane is over 25 times more effective than CO2 at trapping heat over a 100-year period. Major sources include livestock farming, rice paddies, and the decomposition of organic waste in landfills (Global Carbon Project, 2022).


3. Nitrous Oxide (N2O): About 300 times more potent than CO2, nitrous oxide emissions come from fertiliser use, industrial processes, and burning fossil fuels and biomass (United Nations Environment Programme, 2022).


4. Fluorinated Gases: Synthetic gases like hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) are used in refrigeration and industrial processes. Though released in smaller quantities, they have a high global warming potential (IPCC, 2021).


Industrial Changes Since the 19th Century


The Industrial Revolution marked a turning point in human history, with profound effects on the environment. Factories, powered by coal, began producing goods on a massive scale, releasing large amounts of CO2. In the 20th century, the widespread use of automobiles and expansion of power plants burning fossil fuels further increased emissions (Energy Policy journal, 2020).


The post-World War II economic boom saw an explosion in consumerism and energy use. By the 1950s, atmospheric CO2 levels had risen from pre-industrial levels of 280 parts per million (ppm) to over 315 ppm. In 2023, this figure surpassed 420 ppm, according to the National Oceanic and Atmospheric Administration (NOAA, 2023).


Deforestation and Agriculture


Human-driven land-use changes have also contributed to climate change. Large-scale deforestation for agriculture or urban development reduces the planet's ability to absorb CO2. Agriculture is another significant contributor, accounting for nearly 24% of global emissions, primarily from livestock and rice cultivation (Food and Agriculture Organization, 2021).


The Role of Energy and Industry


Energy production accounts for about 73% of global emissions, with coal being the single largest contributor (IEA, 2021). The shift towards renewable energy sources, such as solar and wind, has begun to reduce dependency on fossil fuels, but progress is slow. Industrial processes, including cement production, are also major sources of CO2 emissions (World Resources Institute, 2022).


Understanding is step one.


The causes of climate change are deeply rooted in human activities, particularly since the Industrial Revolution. The enhanced greenhouse effect, driven by increased emissions of CO2, CH4, N2O, and other gases, has resulted in global warming and disrupted climate systems. Addressing these challenges requires a combination of reducing emissions, transitioning to sustainable energy, and protecting natural carbon sinks. Understanding the causes is the first step towards a more sustainable future.


Observed and Predicted Effects of Climate Change

Takeaways

  • We already see effects scientists predicted, such as the loss of sea ice, melting glaciers and ice sheets, sea level rise, and more intense heat waves.

  • Scientists predict global temperature increases from human-made greenhouse gases will continue. 

  • Severe weather damage will also increase and intensify.



Climate change has already caused profound impacts on natural systems and human societies, with further effects expected as global temperatures rise. This document explores the evidence of changes observed so far, alongside predictions for the future, supported by academic sources.


Observed Effects of Climate Change


Rising Temperatures


Global temperatures have increased by approximately 1.1°C since pre-industrial times (IPCC, 2021). This rise has led to noticeable shifts in weather patterns, prolonged heatwaves, and record-breaking temperatures in many regions. For instance, Europe experienced its hottest summer on record in 2023, with countries like Italy and Greece enduring temperatures exceeding 45°C (World Meteorological Organization, 2023).


Melting Ice and Rising Sea Levels


Arctic sea ice has declined significantly, with summer ice cover shrinking by about 13% per decade since 1979 (National Snow and Ice Data Center, 2023). The Greenland and Antarctic ice sheets are also losing mass at unprecedented rates. This melting contributes to sea level rise, which has averaged 3.7 mm per year over the last two decades (NASA, 2022).


Changes in Precipitation Patterns


Climate change has altered global precipitation patterns, leading to more intense storms, floods, and prolonged droughts. For example, the Horn of Africa has faced recurring droughts, devastating agriculture and causing widespread famine (UNICEF, 2023). Conversely, countries like Pakistan have experienced catastrophic flooding, such as the 2022 floods that displaced millions and caused billions in damages (World Bank, 2023).


Impacts on Ecosystems and Biodiversity


Rising temperatures have disrupted ecosystems, with many species struggling to adapt. Coral reefs, vital marine ecosystems, have suffered mass bleaching events due to ocean warming, with the Great Barrier Reef losing 50% of its coral cover since 1995 (Australian Institute of Marine Science, 2022). On land, shifts in habitat ranges threaten species like polar bears, whose survival depends on sea ice.


Human Health and Livelihoods


Heatwaves and extreme weather events have increased mortality rates and exacerbated health issues, particularly in vulnerable populations. The World Health Organization (WHO, 2022) estimates that climate change contributes to 250,000 additional deaths annually due to malnutrition, malaria, and heat stress. Agricultural productivity has also been impacted, with crop failures and food insecurity becoming more common.


Predicted Effects of Climate Change



More Extreme Weather


As temperatures continue to rise, extreme weather events are expected to become more frequent and severe. The IPCC (2021) predicts that heatwaves will increase in intensity and duration, while tropical cyclones will bring heavier rainfall, causing further damage to infrastructure and livelihoods.


Accelerated Sea Level Rise


If current emission trends continue, sea levels could rise by up to 1 metre by 2100 (IPCC, 2021). This would inundate low-lying coastal areas, displacing millions of people and threatening cities such as Jakarta, New York, and Dhaka. Small island nations, like the Maldives, face the existential threat of submersion.


Ocean Warming and Acidification


The oceans absorb about 90% of excess heat from global warming, leading to rising ocean temperatures. This affects marine ecosystems, including fish stocks vital for global food security. Additionally, increased CO2 absorption by oceans leads to acidification, which harms shell-forming species and disrupts marine food chains (NOAA, 2022).


Threats to Biodiversity


Biodiversity loss is expected to accelerate, with up to one million species at risk of extinction due to climate change and habitat destruction (IPBES, 2019). Ecosystems like rainforests and tundras face irreversible changes, reducing their capacity to act as carbon sinks and exacerbating climate feedback loops.


Economic and Social Impacts


The economic costs of climate change are projected to rise sharply. The World Bank (2022) estimates that climate-related disasters could push an additional 132 million people into poverty by 2030. Infrastructure damage, decreased agricultural yields, and increased health costs will strain national economies, particularly in developing countries.


Tipping Points and Feedback Loops


Scientists warn of potential tipping points, where small changes trigger large, irreversible impacts. For example, the melting of permafrost could release vast quantities of methane, a potent greenhouse gas, further accelerating warming (Nature, 2020). Other concerns include the collapse of the Amazon rainforest and disruption of ocean currents like the Atlantic Meridional Overturning Circulation (AMOC).


Expected Future Changes up to 2050 and Beyond


As the global temperature continues to rise, significant changes are predicted in the coming decades. By 2050, it is expected that:


1. Food Security Will Be Severely Impacted: Crop yields for staples such as wheat, maize, and rice could decline by 10-25% in regions like Sub-Saharan Africa and South Asia due to increased heat stress and erratic rainfall (FAO, 2022). Rising temperatures and pests migrating to new regions will further exacerbate this trend.


2. Increased Water Scarcity: By 2050, over 5 billion people could experience water shortages due to reduced freshwater availability, caused by the melting of glaciers and decreased rainfall in key regions (UNESCO, 2022). Major rivers like the Ganges and Yangtze are at risk of diminished flow.


3. Health Impacts Will Intensify: Higher temperatures will lead to the proliferation of diseases such as malaria and dengue fever, particularly in tropical and subtropical areas (Lancet Countdown on Health and Climate Change, 2023). Heat-related illnesses and deaths are also expected to increase, particularly among vulnerable populations.


4. Urban Areas Will Face Greater Risks: Cities are particularly vulnerable to the effects of climate change. Rising temperatures, urban heat islands, and more frequent flooding could overwhelm infrastructure and lead to large-scale displacement (C40 Cities, 2023).


5. Mass Displacement: Climate migration is projected to increase, with an estimated 200 million people displaced by climate impacts by 2050 (World Bank, 2021). This includes individuals fleeing rising sea levels, desertification, and extreme weather events.


6. Energy Systems Under Pressure: The demand for cooling during heatwaves will strain energy systems, while changing weather patterns will disrupt renewable energy production, such as hydropower and wind energy (IEA, 2023).


Long-Term Changes Beyond 2050


Beyond 2050, the impacts of climate change become increasingly severe if mitigation efforts fail. Warming scenarios predict that:


1. Global Warming Exceeding 2°C: If emissions are not significantly reduced, global warming could exceed 2°C by 2100, triggering widespread ecological and economic collapse (IPCC, 2021).


2. Irreversible Ecosystem Damage: Critical ecosystems like the Amazon rainforest may reach a tipping point where they transition from being carbon sinks to carbon sources, releasing vast amounts of CO2 (Nature, 2022).


3. Collapse of Ice Sheets: The complete melting of the Greenland and West Antarctic ice sheets would raise global sea levels by over 10 metres, reshaping coastlines and submerging major cities (Science Advances, 2022).


4. Uninhabitable Regions: Parts of the Middle East and South Asia could experience wet-bulb temperatures exceeding human survivability limits, making them uninhabitable (Environmental Research Letters, 2022).


The Importance of Mitigation and Adaptation


Addressing the effects of climate change requires both mitigation—reducing greenhouse gas emissions—and adaptation—adjusting to unavoidable changes. International agreements like the Paris Agreement aim to limit global warming to well below 2°C, but achieving this goal requires urgent action. Investments in renewable energy, reforestation, and sustainable agriculture are critical, as is strengthening infrastructure to withstand extreme weather. Local and global strategies must work hand-in-hand to create resilient communities.


A word for the future


The observed effects of climate change are already profound, impacting natural systems, human health, and economies. If global temperatures continue to rise, these challenges will intensify, with potentially catastrophic consequences. Predictions for the future underscore the urgency of global action to mitigate emissions and adapt to a changing climate. By acting decisively now, humanity can reduce the worst impacts and build a more sustainable and resilient future. In the current global context of a post-Trump election in November 2024, the outlook is a little bleaker - some observers now recognise that the target to keep the world below a 1.5 C increase will now be missed, but there is a lot to still play for - can we keep the temperature below 1.6, 1.7? - and climate adaptation through the green economies will happen in spite of events in the US. The key is to provide affordable and scalable energy to all of humanity and limit climate change to levels we can adapt to and cope with. Can we do it?


Yes is my answer.




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