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Climate change, what is it actually

Climate change is debatably one of the most important topics at the moment, but what does it actually mean? Have you also wondered: What is climate change actually? Is it real? Should I be worried? These are questions many people wonder about.

To answer these and other questions about climate change, we first have to start at the basis. What is climate?

 

Weather vs Climate

The confusion of climate with weather is quite easily made. The term weather describes the conditions observed on a day to day basis. You can think of the weather forecasts presented on TV, in the newspapers, and on your weather app each day.

Climate on the other hand, as stated by the leading group of scientists that study climate change – the intergovernmental panel on climate change (IPCC) – describes the average weather conditions in a region over a long period of time. Climate represents the average day to day weather over long periods of time, often about 30 years.

Now we are sure everyone understands the difference between weather and climate, we can dig into the question: what is climate change?

 

Two types of climate change

Climate change can actually literally be interpreted as a change in the average climate over long periods of time, time periods of decades. This change can be identified by, for example, a change in the average mean temperature.

When looking at the history of our planet, we see that the climate is actually ever-changing. We know, for example, that multiple ice ages have occurred on Earth. The most recent ice age ended only 11 700 years ago, and is just one of many that have occurred on Earth. So why do we currently worry about climate change?

Scientists are worried about the consequences of the current climate change because of the rate at which climate change occurs at the moment. But not just the rate of change, also its source. Climate change can be classified into two broad categories. Natural climate change, and human induced climate change.

 

Sun shining through a twig

 

Natural climate change

The climate on Earth (and actually all of life that occurs on Earth) is powered by radiation that comes from the Sun. Changes in the received radiation from the sun can consequently severely affect the Earth’s climate. Changes in radiation are caused by changes in the orbit of the Earth around the sun.

The Earth’s movement in our solar system can be described by three different patterns (also known as the Milankovitch Cycles). At the moment, we only have to worry about one of these, as the others mainly influence the seasons. The cycle of importance is called the eccentricity of the Earth.

The Earth does not orbit the sun in a perfectly circular motion, but actually follows more of an elliptical shape. However, more importantly, the shape of the Earth’s orbit changes over time. The Earth’s orbit changes between an almost circular motion and an elliptical motion in cycles over astounding time periods of 100 000 and 413 000 years.

When the earth orbit follows an almost circular shape, the radiation Earth receives year round is almost constant. However, when the Earth follows a more elliptical shape, the difference in radiation the earth receives from the sun can be as large as 30% during that year.

This change in the radiation the Earth receives over time can be seen as the driving force behind natural climate change.

 

Human induced climate change

Natural climate change thus occurs over long periods of time (100 to 413 thousand years). These long periods of time allowed life on Earth to adapt quite successfully. For example, by migrating towards the equator during ice ages, and back towards the poles during warm periods, such as the current period we live in. If we now look at the rate at which the current climate changes, we would see that the climate strongly changes per decade!

During the last years, there has been one “famous” figure that has been used by scientists to indicate that climate change does occur, as well as by climate skeptics to show that it all is just a scam. The figure is often referred to as the hockey stick figure, due to its shape.

I have made a similar figure below by use of the same data that is used by IPCC (1). I have plotted the temperature anomaly from 1880 til 2017. Temperature anomaly basically means the change in temperature with respect to the average temperature (the average temperature from the years 1951 through 1980).

 

Temperature anomaly over the years 1880 til the present

 

I think, that if you look at the figure as a whole, you undoubtedly see that the temperature has increased tremendously in the last few decades. Climate skeptics however, often tried to use this figure to cast doubt with people by showing just a subset of the figure.

I have put a red circle in the graph, to indicate the part climate skeptics tend to focus on. They often extract this part of the figure to show that there is no climate change or that it has stabilized. But when you see the complete course of temperature, it becomes undisputedly clear that Earth’s climate has in fact changed quite strongly over the last decades.

Some other important indicators of climate change besides the observed increase in temperature are:

  • Acidification of the oceans
  • Changes in the atmospheric water vapor
  • Sea level rise
  • Shrinking of sea ice
  • Higher occurrence of extreme weather events

 

Main causes behind human induced climate change

As I explained previously, the Earth is driven by radiation from the sun. Most of this radiation gets absorbed in the atmosphere by greenhouse gases, gases such as carbon dioxide, water vapor, and methane. Part of this absorbed radiation is subsequently re-emitted to Earth, resulting in an increase in the temperature.

If there would not be any greenhouse gases present in the atmosphere, the average temperature on Earth would be -18 degrees Celsius, instead of the current pleasant temperature of 15 degrees celsius. Without greenhouse gases, life as we know it would not be possible here on Earth!

The occurrence of greenhouse gases in the atmosphere is thus actually quite useful for us. The problem now is the fact that we have been and still are emitting an insane amount of greenhouse gases into the atmosphere. More greenhouse gases in the atmosphere basically means a higher amount of radiation that is absorbed, and thus a higher amount that is emitted back to Earth. Eventually, this increases the temperature here on Earth.

A higher concentration of greenhouses thus translates directly into an increased temperature on Earth, and thus in a change of our climate. This increase in greenhouse gases is the most important driver behind human induced climate change.

Some important sources of greenhouse gas emissions are:

  • The destruction of forests
  • Most agricultural practices, such as rice fields and the use of fertilisers
  • Burning of fossil fuel by the industry and by cars
  • An increase in livestock

We hope you have learned something from this post. If some parts are unclear or if you happen to have any questions, feel free to ask them below! And keep an eye out for more in-depth posts about climate change on our blog in the future.

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