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Quick Guide to Climate Change

So what is Climate Change?

Simply, Climate Change refers to long-term shifts in temperatures and weather patterns on Earth.

These shifts may be natural, such as through variations in the solar cycle. BUT, since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels like coal, oil and gas.

Climate Change data & thoughts from 2021

The UN's World Meteorological Organization analysed the six main global temperature data sets and found that 2021 was the seventh hottest year to date, at 1.11°C The past seven years were the warmest on record as climate change continued apace, despite the cooling effect of the La Niña weather pattern in 2021.

The seven warmest years have occurred since 2015 and is precisely what we would expect to see due to human-caused planetary warming.

Governments at the COP26 climate summit in November reaffirmed their commitment to trying to hold temperature rises to 1.5°C and well below 2°C at worst. But emissions reductions pledges currently have the world on course for 2.4°C or more. 2021 is the seventh year in a row where temperatures have been more than 1°C above pre-industrial levels.

While only the seventh warmest year on average globally, 2021 saw climate scientists shocked by several temperature records broken by much larger margins than usual in some places, such as the near -50°C record set in Lytton, Canada. Previous research showed this event would have been “virtually impossible” without climate change. “Climate change impacts and weather-related hazards had life-changing and devastating impacts on communities on every single continent,” said Petteri Taalas at the WMO in a statement.

Although not a record for surface air temperatures, 2021 was another record-breaking year for heat content in the upper levels of the oceans, which are absorbing much of the carbon dioxide emitted by humans and the heat that this gas traps.

The cooling effect of the La Niña weather pattern is expected to give way later this year to its opposite, El Niño, which was responsible for 2016 being the hottest year on record. The UK Met Office, which holds one of the six data sets examined by the WMO, forecasts that 2022 will be 1.09°C above pre-industrial levels.

Greenhouse gases and the greenhouse effect

Some gases in the Earth's atmosphere trap heat and stop it escaping into space. We call these, “Greenhouse gases". These gases act as a warming blanket around the Earth, known as the “Greenhouse effect”.

Greenhouse gases come from both human and natural sources. Gases like carbon dioxide, methane, and nitrous oxide also naturally occur in the atmosphere. Others, such as chlorofluorocarbons (CFCs), are only produced by human activity.

When short-wave radiation from the sun reaches Earth, most of it passes straight through and hits the surface of The Earth. The Earth absorbs most of this radiation and gives off longer-wavelength infrared radiation.

The “greenhouse gases“ absorb some of this infrared radiation, instead of it passing straight back out into space. The Earth’s atmosphere then emits radiation in all directions, sending some of it back to the surface, causing the planet to heat up. This process is known as the “greenhouse effect”.

The “greenhouse effect” is actually critical to our survival. In fact, without greenhouse gases, Earth would be about 30 degrees colder than it is today so… Without “greenhouse gases” and their warming effect, we wouldn't be able to survive.

However, since the Industrial Revolution, we've been adding more and more greenhouse gases into the air, trapping even more heat. Instead of keeping Earth at a warm, stable temperature, the ”greenhouse effect” is heating the planet at a much faster rate. We call this the "enhanced greenhouse effect" and this is the main cause of climate change.

So basically, a climate balance is needed… TOO MUCH, TOO HOT! and TOO LITTLE, TOO COLD! 

Natural changes to the climate

The leading cause of climate change is human activity and the release of "too many" greenhouse gases. However, there are lots of natural causes that also lead to changes in the climate system.

Natural cycles can cause the climate to alternate between warming and cooling. There are also natural factors that force the climate to change, like volcanoes and the Sun. Even though these natural causes contribute to climate change, we now know that they are not the primary cause, based on scientific evidence.

Some of these natural cycles are: 

Milankovitch Cycles - As Earth travels around the sun, its path and the tilt of its axis can change slightly. These changes, called Milankovitch cycles, affect the amount of sunlightfrom the sun that falls on Earth. This can cause the temperature of Earth to change. However, these cycles take place over tens or hundreds of thousands of years and are unlikely to be causing the changes to the climate that we are seeing today.

El Niño Southern Oscillation (ENSO) – ENSO is a pattern of changing water temperatures in the Pacific Ocean. In an 'El Niño' year, the global temperature warms up, and in a 'La Niña' year, it cools down. These patterns can affect the global temperature for a short amount of time (months or years) but cannot explain the persistent warming that we see today.

Solar irradiance – Changing energy from the sun has affected the temperature of Earth in the past. However, we have not yet seen anything strong enough to change our climate.

Any increase in solar energy would make the entire atmosphere of Earth warm, but we can only see warming in the bottom layer.

Volcanic eruptions – Volcanoes have a mixed effect on our climate. Eruptions produce aerosol particles that cool Earth, but they also release carbon dioxide, which warms it.

Volcanoes produce 50 times less carbon dioxide than humans do, so we know they are not the leading cause of global warming. On top of this, cooling is the dominant effect of volcanic eruptions, not warming.

Human changes to the climate

Humans cause climate change by releasing carbon dioxide and other greenhouse gases into the air. Today, there is more carbon dioxide in the atmosphere than there ever has been in at least the past 2 million years. During the 20th and 21st century, the level of carbon dioxide rose by 40%.

We produce greenhouse gases in lots of different ways:

Burning fossil fuels – Fossil fuels such as oil, gas, and coal contain carbon dioxide that has been 'stored away' in the ground for thousands of years. When we take these out of the land and burn them, we release the "stored away" carbon dioxide into the air.

Deforestation – Forests remove and store carbon dioxide from the atmosphere. Trees sequester (absorb) carbon dioxide. Cutting them down means that carbon dioxide builds up quicker since there are less trees to absorb it. Not only that, trees release the carbon they stored when we burn them. Just like burning fossil fuels does.

Agriculture – Planting crops and rearing animals releases many different types of greenhouse gases into the air. For example, animals produce methane, which is 30 times more powerful than carbon dioxide as a greenhouse gas. The nitrous oxide used for fertilisers is ten times worse and is nearly 300 times more potent than carbon dioxide! 

Cement – Producing cement is another contributor to climate change, causing 2% of our entire carbon dioxide emissions. 

Impacts of climate change

Human activity

From releasing greenhouse gases and aerosols into the atmosphere, to changing the use of land – is the main driver of climate change. This has a range of impacts on the climate system, ecosystems, and people.

Changes to the climate system

Rising ocean levels – Rising temperatures are causing glaciers and ice sheets to melt, adding more water to the oceans and causing the ocean level to rise. Oceans absorb 90% of the extra heat from global warming: warmer water expands, and so our oceans are taking up more space.

Ocean acidification – Ocean acidification occurs when the ocean absorbs carbon dioxide and becomes more acidic. It is often called the 'evil twin' of climate change.

Extreme weather events – Climate change is causing many extreme weather events to become more intense and frequent, such as heatwaves, droughts, and floods.

Climate change can also affect people and ecosystems

Flooding of coastal regions – Coastal cities are at risk from flooding as sea levels continue to rise. 

Food insecurity – High temperatures, extreme weather events, flooding, and droughts can damage farmland. This makes it difficult for farmers to grow crops and means that their yield of crops each year is uncertain.

Conflict and climate migrants – Climate change is a stress multiplier – it can take existing problems, such as lack of food or shelter, and make them worse. This can cause people to fight over resources (food, water, and shelter), or to migrate.

Damage to marine ecosystems – Rising ocean temperatures, ocean acidification, and ocean anoxia (lack of oxygen) are damaging to marine life such as fish and coral reefs. 

Are humans responsible for climate change?

When looking at all the evidence, there is a large scientific consensus that humans are the leading cause of climate change. In their latest report, the Intergovernmental Panel on Climate Change stated unequivocally that human activity is the main cause of global warming.

Natural climate cycles can change the temperature of Earth, but the changes we are seeing are happening at a scale and speed that natural cycles cannot explain. These cycles affect the global temperature for years, or sometimes just months, not the 100 years that we have observed. Meanwhile, longer-term changes like Milankovitch cycles and solar irradiance take thousands and thousands of years.

There are lots of things that affect climate change, but the evidence is irrefutable. Human activity, such as burning fossil fuels, how we farm, fertilize and use our land, is the leading cause of climate change.

How can we return to a balanced climate?

Reduce global greenhouse gas emissions. The most crucial step to limit and balance climate change is to make big and rapid reductions in global greenhouse gas emissions.

There are many different ways this can be done and governments, businesses, organisations and individuals around the world can all contribute.

In June 2019, the UK became the world’s first major economy to pass a law committing the country to a target of "net zero" emissions by 2050.


Next read... How can we humans help climate change?