Many people do not know what it really amounts to, either due to unreliable sources or deliberate misinformation, which has led to a series of myths about climate change. In these pages, we tackle the subject from an objective, scientific viewpoint, discussing the causes and consequences of climate change and how it should be tackled.
First, we need to clarify two concepts often mistaken for synonyms: climate change and global warming. There is an important difference between them, however, given that it is global warming that causes climate change. As the planet’s temperature rises more than it would naturally, the climate varies.
Although it is certain that Earth has naturally warmed up and got colder during other eras, such cycles have always been much slower, taking millions of years, whereas now, within a period of just 200 years, we are reaching levels that in the past brought about extinctions.
Before going over the causes and effects of climate change, let's explain why you don't care about climate change:
Global warming is caused by the greenhouse effect, a natural process by which the atmosphere retains some of the Sun’s heat, allowing the Earth to maintain the necessary conditions to host life. Without the greenhouse effect, the average temperature of the planet would be -180C.
The problem is that daily human activities maximize the greenhouse effect, causing the planet’s temperature to increase even more.
Causes behind global warming
- Carbon dioxide: caused by the burning mainly of fossil fuels in electricity generation, transport, heating, industry and construction.
- Methane: from livestock, rice farming and waste tips.
- Nitrogen oxide: caused by excess use of fertilizers and industrial activity.
HCFCs: gas of anthropogenic origin (result of human activities) replacing CFCs. Harmless to the ozone layer, but increases the greenhouse effect.
Forests are natural carbon sinks, absorbing CO2 through photosynthesis and returning oxygen to the atmosphere.
The oceans are also carbon sinks, absorbing up to 50 % of CO2 The problem is that, when they reach their limit, the ocean acidifies and causes death and disease among marine flora and fauna.
An increasingly numerous population needs more and more resources, which speeds up the increase in greenhouse gas emissions from all production processes.
Experts agree that the Industrial Revolution was the turning point when emissions of greenhouse effect gases
What is climate change and why does it matter?
Find out what climate change is, why it matters and what it could mean for our collective future.
What are weather, climate and climate change?
Weather refers to atmospheric conditions, such as rain or snow, happening in a place at a specific moment in time. Climate is how much, on average, a type of weather will occur over a longer period.
Dr Joeri Rogelj is a climate scientist at Imperial College London's Grantham Institute who has contributed to and led several major climate change assessments. He explains, 'Climate change is how the characteristics of the weather we experience in a certain place change.
'It can get hotter or wetter on average or have more concentrated rain in a short period, but then get longer dry periods. All of that can be a result of climate change.'
Global warming is a term used interchangeably with climate change, although the latter is preferred because the warming atmosphere and oceans are just some of the effects we see.
'It's not just about temperature. Places are also becoming wetter or drier, and in some the seasons are moving. Most importantly, in a few regions and seasons, it may actually at times be cooler than we're used to. That's confusing if you just talk about global warming.'
This is Typhoon Utor, which affected the Philippines and China in 2013. It caused considerable damage and loss of life. Climate change influences most weather events, including tropical storms and hurricanes. © NASA Goddard Space Flight Center via Flickr (CC BY 2.0)
The main driver of current climate change is the emission of greenhouse gases, most importantly carbon dioxide and methane. These are primarily released when fossil fuels are burnt. Meat and dairy production, producing cement and some industrial processes, such as the production and use of fertilisers, also emit greenhouse gases.
Greenhouse gases trap heat in our atmosphere. Since the mid-nineteenth century, the world has emitted over 2.2 trillion tonnes of carbon dioxide.
Joeri explains, 'Energy from the Sun falls on our planet and normally gets reflected back as infrared radiation. But instead of escaping back out into space, this radiation gets absorbed by molecules of greenhouse gases, which then emit them in all directions.'
This process causes more heat to be kept near Earth's surface, warming our world.
How do we know climate is changing?
There are measuring stations all around the world that keep track of air and sea temperature. From these measurements it's clear that temperatures are rising.
'There are many more indicators that tell us that the Earth is warming. For example, on a warming planet we would expect polar ice caps and glaciers to melt. It is clearly observed that those are melting,' explains Joeri.
This image of an iceberg in McMurdo Sound was captured in 2017 as part of NASA's Operation IceBridge. This is an ongoing airborne mission to monitor changes in polar ice. © NASA Goddard Space Flight Center via Flickr (CC BY 2.0)
We know that greenhouse gases are causing change. Thanks to studies that look at how carbon dioxide absorbs infrared radiation, for example, there is a scientific understanding of how the planet would warm as a result of emissions. This has allowed climate scientists to discount the theory that global warming is being caused by an increase in the Sun's intensity, for example.
It's also known that greenhouse gases are primarily emitted by fossil fuel combustion.
'To burn carbon and produce carbon dioxide, you need oxygen. The amount of oxygen that is in the atmosphere is reducing at exactly the right amount for the increase in carbon dioxide to be caused by combusting fossil fuels,' explains Joeri.
There is additional evidence in the ratios of different types of carbon. Fossil fuels are, essentially, ancient plants. Plants now and in the past preferentially take up carbon-12. In normal conditions, the ratio between carbon-12 and carbon-13 is constant.
'What we can see is that the ratio of carbon-13 in our atmosphere is going down at exactly the rate you would predict if the carbon dioxide increase was due to burning fossil fuels.'
Scientists predict that climate change will cause extreme weather events such as wildfires, floods and hurricanes to become worse © Quarrie Photography via Flickr (CC BY-NC-ND 2.0)
Climate change does not have the same effects everywhere. The planet is generally getting hotter, but some regions and seasons can at times be temporarily cooler. Some places will see drawn-out seasons, while others may experience concentrated bursts of extreme weather.
Extreme weather events – such as hurricanes, heatwaves, drought, wildfires and floods – are predicted to become more intense and frequent.
What Is Climate Change?
Weather describes the conditions outside right now in a specific place. For example, if you see that it’s raining outside right now, that’s a way to describe today’s weather. Rain, snow, wind, hurricanes, tornadoes — these are all weather events.
Climate, on the other hand, is more than just one or two rainy days. Climate describes the weather conditions that are expected in a region at a particular time of year.
Is it usually rainy or usually dry? Is it typically hot or typically cold? A region’s climate is determined by observing its weather over a period of many years—generally 30 years or more.
So, for example, one or two weeks of rainy weather wouldn’t change the fact that Phoenix typically has a dry, desert climate. Even though it’s rainy right now, we still expect Phoenix to be dry because that's what is usually the case.
Want to know more about the difference between weather and climate? Take a look at this video!
Alaska's Muir glacier in August 1941 and August 2004. Significant changes occurred in the 63 years between these two photos. Credit: USGS
Climate change describes a change in the average conditions — such as temperature and rainfall — in a region over a long period of time. For example, 20,000 years ago, much of the United States was covered in glaciers. In the United States today, we have a warmer climate and fewer glaciers.
Global climate change refers to the average long-term changes over the entire Earth. These include warming temperatures and changes in precipitation, as well as the effects of Earth’s warming, such as:
- Rising sea levels
- Shrinking mountain glaciers
- Ice melting at a faster rate than usual in Greenland, Antarctica and the Arctic
- Changes in flower and plant blooming times.
Earth’s climate has constantly been changing — even long before humans came into the picture. However, scientists have observed unusual changes recently. For example, Earth’s average temperature has been increasing much more quickly than they would expect over the past 150 years.
Want to know more about how we know climate change is happening? Check it all out here!
How Much Is Earth’s Climate Changing Right Now?
Graph of change in annual global temperatures, compared to the average of global annual temperatures from 1880-1899. Credit: NASA's Goddard Space Flight Center
Some parts of Earth are warming faster than others. But on average, global air temperatures near Earth's surface have gone up about 2 degrees Fahrenheit in the past 100 years. In fact, the past five years have been the warmest five years in centuries.
Many people, including scientists, are concerned about this warming. As Earth’s climate continues to warm, the intensity and amount of rainfall during storms such as hurricanes is expected to increase. Droughts and heat waves are also expected to become more intense as the climate warms.
When the whole Earth’s temperature changes by one or two degrees, that change can have big impacts on the health of Earth's plants and animals, too.
What Causes Climate Change?
A simplified animation of the greenhouse effect. Credit: NASA/JPL-Caltech
There are lots of factors that contribute to Earth’s climate. However, scientists agree that Earth has been getting warmer in the past 50 to 100 years due to human activities.
What is climate change?
Climate change is the long-term shift in average weather patterns across the world. Since the mid-1800s, humans have contributed to the release of carbon dioxide and other greenhouse gases into the air. This causes global temperatures to rise, resulting in long-term changes to the climate.
Climate change evidence
How are humans changing the climate?
In the 11,000 years before the Industrial Revolution, the average temperature across the world was stable at around 14°C. The Industrial Revolution began in the mid-1800s when humans began to burn fossil fuels such as coal, oil, and gas for fuel.
Burning fossil fuels produces energy, but also releases greenhouse gases such as carbon dioxide, methane, and nitrous monoxide into the air. Over time, large quantities of these gases have built up in the atmosphere.
For example, the level of carbon dioxide in the atmosphere rose by 40% during the 20th and 21st century and is now over 400ppm (parts per million). This level of carbon dioxide is higher than at any time in the past 800,000 years.
This plot shows the global temperature change from 1850 to 2018, compared to the 1961-1990 average temperature.
This graph shows the rising level of carbon dioxide in our atmosphere since 1960, measured by the Mauna Loa Observatory in Hawaii.
Once in the atmosphere, greenhouse gases such as carbon dioxide form a 'blanket' around the planet. This blanket traps the heat from the sun and causes the earth to heat up.
This effect was noticed as far back as the 1980s. In 1988, the International Panel on Climate Change (IPCC) was set up to provide governments with information to tackle climate change.
Evidence has shown that the high levels of greenhouse gases in the atmosphere are the leading cause of increasing global temperatures.
Scientists have been able to rule out natural events as causes of climate change, such as volcanic activity, changes in solar activity, or natural sources of CO2. These may, however, have a small effect, on top of human contributions.
A really simple guide to climate change
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Media captionOur Planet Matters: Climate change explained
While Covid-19 has shaken much of human society, the threat posed by global warming has not gone away.
Human activities have increased carbon dioxide emissions, driving up temperatures. Extreme weather and melting polar ice are among the possible effects.
What is climate change?
The Earth's average temperature is about 15C but has been much higher and lower in the past.
There are natural fluctuations in the climate but scientists say temperatures are now rising faster than at many other times.
This is linked to the greenhouse effect, which describes how the Earth's atmosphere traps some of the Sun's energy.
Solar energy radiating back to space from the Earth's surface is absorbed by greenhouse gases and re-emitted in all directions.
This heats both the lower atmosphere and the surface of the planet. Without this effect, the Earth would be about 30C colder and hostile to life.
Scientists believe we are adding to the natural greenhouse effect, with gases released from industry and agriculture trapping more energy and increasing the temperature.
This is known as climate change or global warming.
What are greenhouse gases?
The greenhouse gas with the greatest impact on warming is water vapour. But it remains in the atmosphere for only a few days.
Carbon dioxide (CO2), however, persists for much longer. It would take hundreds of years for a return to pre-industrial levels and only so much can be soaked up by natural reservoirs such as the oceans.
Most man-made emissions of CO2 come from burning fossil fuels. When carbon-absorbing forests are cut down and left to rot, or burned, that stored carbon is released, contributing to global warming.
Since the Industrial Revolution began in about 1750, CO2 levels have risen more than 30%. The concentration of CO2 in the atmosphere is higher than at any time in at least 800,000 years.
Other greenhouse gases such as methane and nitrous oxide are also released through human activities but they are less abundant than carbon dioxide.
What is the evidence for warming?
The world is about one degree Celsius warmer than before widespread industrialisation, the World Meteorological Organization (WMO) says.
The 20 warmest years on record all occurred in the past 22 years, with 2015-18 making up the top four.
Across the globe, the average sea level increased by 3.6mm per year between 2005 and 2015.
Most of this change was because water increases in volume as it heats up.
However, melting ice is now thought to be the main reason for rising sea levels. Most glaciers in temperate regions of the world are retreating.
And satellite records show a dramatic decline in Arctic sea-ice since 1979. The Greenland Ice Sheet has experienced record melting in recent years.
Satellite data also shows the West Antarctic Ice Sheet is losing mass. A recent study indicated East Antarctica may also have started to lose mass.
The effects of a changing climate can also be seen in vegetation and land animals. These include earlier flowering and fruiting times for plants and changes in the territories of animals.
How much will temperatures rise in future?
What is climate change?
Climate change, also called global warming, refers to the rise in average surface temperatures on Earth.
An overwhelming scientific consensus maintains that climate change is due primarily to the human use of fossil fuels, which releases carbon dioxide and other greenhouse gases into the air.
The gases trap heat within the atmosphere, which can have a range of effects on ecosystems, including rising sea levels, severe weather events, and droughts that render landscapes more susceptible to wildfires.
Is climate change real?
There is broad-based agreement within the scientific community that climate change is real. The U.S. Environmental Protection Agency, the National Aeronautics and Space Administration, and the National Oceanic and Atmospheric Administration concur that climate change is indeed occurring and is almost certainly due to human activity.
What are the causes of climate change?
The primary cause of climate change is the burning of fossil fuels, such as oil and coal, which emits greenhouse gases into the atmosphere—primarily carbon dioxide. Other human activities, such as agriculture and deforestation, also contribute to the proliferation of greenhouse gases that cause climate change.
While some quantities of these gases are a naturally occurring and critical part of Earth’s temperature control system, the atmospheric concentration of CO2 did not rise above 300 parts per million between the advent of human civilization roughly 10,000 years ago and 1900. Today it is at about 400 ppm, a level not reached in more than 400,000 years.
Increased burning of fossil fuels contributes to climate change.
(Photo: Chris Conway/Getty Images)