Understanding Global Warming and Climate Change: Causes and Effects

Every year, we hear about record-breaking heatwaves, catastrophic floods, vanishing glaciers, and species disappearing from the planet. These are not isolated incidents – they are symptoms of two closely connected phenomena: global warming and climate change. Understanding what drives them, and what they mean for the planet and for human societies, is no longer optional. It is one of the most pressing literacy requirements of our time.

Weather vs. climate: why the distinction matters
The greenhouse effect: essential but now enhanced
Human activities driving global warming
Burning fossil fuels
Deforestation
Agriculture and livestock farming
Industrial fluorinated gases
Consequences of global warming: a cascade of effects
Climatic shifts and extreme weather
Biodiversity loss
Socioeconomic impacts
The urgency of the 1.5°C threshold

Weather vs. climate: why the distinction matters

People often use “weather” and “climate” interchangeably, but the two are fundamentally different. Weather refers to short-term atmospheric conditions – the temperature on a given afternoon, whether it rained last Tuesday, or how strong the wind was this morning. Climate, on the other hand, is the long-term pattern of weather in a region, typically measured over 30 years or more. As a familiar saying goes: “Climate is what you expect; weather is what you get.”

This distinction matters because a single cold winter does not disprove global warming, just as one hot summer does not confirm it. Climate change refers to long-term, sustained shifts in these patterns – rising average temperatures, altered rainfall cycles, more frequent extreme events – that go far beyond natural year-to-year variability. According to NSW Government’s AdaptNSW, when we compare today’s rate of climate change with historical natural cycles, the current pace is demonstrably higher – a clear indicator of human influence rather than natural fluctuation alone.

The greenhouse effect: essential but now enhanced

To understand global warming, you first need to understand the greenhouse effect – a natural and essential process without which life on Earth would not exist.

When the Sun’s energy reaches Earth, the planet absorbs it and then releases it back as infrared heat. Certain gases in the atmosphere – carbon dioxide (CO₂), methane, nitrous oxide, and water vapour – trap a portion of this heat, preventing it from escaping into space. Australia’s Department of Climate Change explains that this natural process keeps Earth’s surface roughly 33°C warmer than it would otherwise be, making it habitable. Without it, the average global temperature would hover around −18°C.

The problem is not the greenhouse effect itself – it is its enhancement due to human activities. Since the Industrial Revolution around 1750, the burning of fossil fuels, large-scale deforestation, and intensive agriculture have dramatically increased the concentrations of greenhouse gases in the atmosphere. This traps more heat than the planet’s systems can handle, steadily pushing global temperatures upward – a process known as the enhanced greenhouse effect.

Human activities driving global warming

The scientific evidence is unequivocal. As the U.S. Energy Information Administration (EIA) notes, the IPCC’s Sixth Assessment Report states that human influence on warming the atmosphere, ocean, and land since pre-industrial times is beyond question. So what are the primary human activities responsible?

Burning fossil fuels

According to the United Nations, fossil fuels – coal, oil, and gas – account for around 68% of global greenhouse gas emissions and nearly 90% of all CO₂ emissions. Electricity generation, transportation, and industrial processes that rely on these fuels are the dominant drivers of rising atmospheric CO₂ levels. The CSIRO notes that global atmospheric CO₂ concentrations grew from 277 parts per million (ppm) in 1750 to 412 ppm by 2020 – and they continue rising.

Deforestation

Forests are natural carbon sinks – they absorb CO₂ from the atmosphere through photosynthesis. When forests are cleared for agriculture, logging, or urban development, two things happen: the stored carbon in trees is released back into the atmosphere, and the landscape loses its capacity to absorb future emissions. The European Commission identifies deforestation as a significant contributor to the greenhouse effect, compounding the damage done by fossil fuel combustion.

Agriculture and livestock farming

Food production is another major source of greenhouse gas emissions. Livestock – particularly cattle and sheep – produce large amounts of methane during digestion. Nitrogen-based fertilisers release nitrous oxide, a greenhouse gas roughly 300 times more potent than CO₂ over a 100-year period. The UN estimates that food production as a whole is a major contributor to climate change, factoring in land clearing, farming machinery, and supply chains.

Industrial fluorinated gases

Fluorinated gases (F-gases) used in refrigeration, air conditioning, and industrial manufacturing are entirely human-made and carry extreme warming potential. The European Parliament notes that some F-gases have a warming effect up to 23,000 times stronger than CO₂, making even small quantities environmentally significant.

Consequences of global warming: a cascade of effects

Global warming does not simply mean warmer summers. Its consequences ripple through natural systems and human societies in interconnected and often devastating ways.

Climatic shifts and extreme weather

As greenhouse gas concentrations rise, so does the global surface temperature. The World Meteorological Organization (WMO) confirmed that 2024 was the warmest year in the 175-year observational record, with global mean temperatures reaching 1.55°C above the pre-industrial average. Each of the past ten years has ranked individually among the ten warmest ever recorded.

Warmer temperatures intensify the water cycle – more evaporation leads to heavier rainfall and flooding in some regions, while others face prolonged drought. The UN reports that destructive storms have become more intense and frequent, as cyclones and hurricanes feed on warmer ocean surfaces. Rising sea levels, driven by thermal expansion of warming oceans and the melting of ice sheets, now directly threaten coastal communities worldwide.

Biodiversity loss

Climate change is one of the fastest-growing threats to the diversity of life on Earth. The United Nations reports that the world is losing species at a rate 1,000 times greater than at any other time in recorded human history, with one million species at risk of extinction in the coming decades. On land, higher temperatures are forcing animals and plants toward higher elevations or polar latitudes – and many cannot move fast enough.

Marine ecosystems face equally serious threats. The Natural History Museum highlights that the mounting climate crisis is causing ice and snow to melt, eroding vital coastal ecosystems and putting between 100 and 300 million people at heightened risk of floods and hurricanes due to the loss of protective coastal habitats like mangroves. In the ocean, warmer waters trigger coral bleaching – a process where corals expel the algae they need to survive. According to the UN, 14% of the world’s coral reefs were lost between 2009 and 2018, mostly due to climate change.

Biodiversity loss also has a direct feedback effect on climate change itself. Forests, peatlands, and ocean habitats serve as carbon sinks. When these ecosystems degrade, their capacity to absorb CO₂ weakens, further accelerating warming.

Socioeconomic impacts

The consequences of global warming are not just ecological – they are profoundly social and economic. The WMO’s State of the Global Climate 2025 report confirms that extreme weather events now cascade into agricultural disruption, migration, and political instability. Food insecurity, displacement, and inequality are increasingly climate-driven outcomes.

Food security: Changing rainfall patterns, prolonged droughts, and more frequent floods are disrupting crop production globally. The WMO documented that weather and climate-related events were responsible for nearly 94% of all disaster displacement over the 2011-2020 decade, and played a direct role in reversing progress on global efforts to end hunger. Globally, acute food insecurity more than doubled – from 149 million people before the COVID-19 pandemic to 333 million in 2023.

Displacement and migration: According to the WMO, tropical cyclones, floods, and droughts in 2024 alone caused the highest number of new displacements in the past 16 years. Slow-onset changes like rising sea levels and land degradation further displace populations over time, disproportionately affecting the most vulnerable communities in low-income and conflict-affected regions.

Economic costs: Infrastructure damage from extreme weather events – floods washing away roads and bridges, wildfires destroying property, storms disrupting supply chains – carries enormous economic costs. The WMO notes that while the number of deaths from extreme events has declined due to improved early warning systems, economic losses have continued to rise sharply.

Health: Rising temperatures are expanding the geographic range of mosquito-borne diseases like dengue fever. Heat stress from extreme heatwaves poses direct threats to human health, particularly for outdoor workers and the elderly. The WMO’s 2025 report includes a dedicated chapter on climate and health, illustrating how shifting temperatures and rainfall patterns are reshaping when, where, and how severely health risks emerge.

Inequality: Climate change disproportionately affects those who have contributed least to it. As research published in Science outlines, failing to address the twin crises of climate change and biodiversity loss will increase poverty, food insecurity, involuntary displacement, and political instability – consequences borne most heavily by developing nations and marginalised communities.

The urgency of the 1.5°C threshold

The international community has recognised that limiting warming to 1.5°C above pre-industrial levels is critical to avoiding the most catastrophic consequences. The European Commission notes that an increase of 2°C is associated with serious negative impacts on the natural environment and on human health and wellbeing, including a much higher risk of dangerous and potentially irreversible changes to the global environment. Yet the WMO confirmed that 2024 was likely the first calendar year to exceed 1.5°C above pre-industrial levels – a threshold once considered a distant warning sign.

Every fraction of a degree matters. At 1.5°C, an estimated 70-90% of coral reefs could be lost. At 2°C, that figure rises to 99%. For mammals, the share that could lose over half their habitat more than doubles between 1.5°C and 2°C of warming. These are not abstract projections – they are measurable thresholds with concrete consequences for both ecosystems and human societies.

The Royal Society summarises the scientific consensus clearly: rigorous analysis of all data and evidence shows that most of the observed global warming over the past 50 years cannot be explained by natural causes, and instead requires a significant role for human activity. The physics are well-understood, the data are robust, and the window for effective action is narrowing.

What do you think? Given that the countries most affected by climate change are often the least responsible for greenhouse gas emissions, how should the global community approach the question of climate justice and shared responsibility? And as biodiversity and climate are now understood to be deeply interdependent, should environmental policy treat them as a single integrated crisis rather than separate problems?

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Table of Contents

Weather vs. climate: why the distinction matters 🔗

The greenhouse effect: essential but now enhanced 🔗

Human activities driving global warming 🔗

Burning fossil fuels 🔗

Deforestation 🔗

Agriculture and livestock farming 🔗

Industrial fluorinated gases 🔗

Consequences of global warming: a cascade of effects 🔗

Climatic shifts and extreme weather 🔗

Biodiversity loss 🔗

Socioeconomic impacts 🔗

The urgency of the 1.5°C threshold 🔗