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 a climate?


Weather vs. Climate

We can easily confuse climate with weather. The term weather describes the conditions observed on a day to day basis. You can think of 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.


Two types of climate change

Climate change is a change in the average climate over long periods of time, time periods of decades. We can identify this change 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 climate change because of its current rate. 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.

Rold Skov forest


Natural climate change

The climate on Earth (and actually all of life that occurs on this planet) 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.

There are three different patterns that can describe the Earth’s movement in our solar system (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 to 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, which 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 allow 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!

Over the past few years, scientists have used one “famous” figure to indicate that climate change does occur. Climate skeptics have used the figure to show that it is all just a scam. Due to its shape, people often refer to the figure as ‘the hockey stick figure.

I have made a similar figure below by use of the same data that are used by IPCC (1). I have plotted the temperature anomaly from 1880 to 2017. Simply speaking, temperature anomaly 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 looking at the figure as a whole, you undoubtedly see a tremendous increase in temperature in the last few decades. Climate skeptics however often tried to use this figure to cast doubt 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 climate change does not exist, 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. The greenhouse gases in the atmosphere – such as carbon dioxide, water vapor, and methane – absorb most of this radiation. 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 however is the fact that we have been, and still are, emitting an extraordinary amount of greenhouse gases into the atmosphere. More greenhouse gases in the atmosphere basically means a higher amount of radiation that is absorbed. This results in a higher amount that is emitted back to Earth. Eventually, this increases the temperature on our planet.

A higher concentration of greenhouses thus translates directly into an increased temperature on Earth, and thus in climate change. This increase in greenhouse gases are 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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