Evidence for Climate Change

It can be hard to understand climate change on an individual level without experiencing the effects of what climate change is doing. On the news, we might see flooding in South Korea or drought in Mexico, but in the UK, the changes are not as drastic. We might sense a warmer summer and more rainfall in the winter, but could this be just natural changes that happen at random? As we look at the evidence for climate change and start to see what the scientists have seen, it will become clear that climate change is not a natural change happening by chance. So, what are the facts? What types of evidence is there? This article will explain all about the evidence for our changing climate. Let's dive in!

Evidence for Climate Change explained

Let's firstly explain a little about climate change. The Earth's climate has been changing naturally in the past because of the interactions between the ocean and the atmosphere, the changes in the earth's orbit, volcanic activity, and changes in the energy from the sun. However, more recently, it is universally agreed that the significant changes in climate are not just because of natural causes. The change in climate has been directly connected to human activity since the mid-1800s. The cause of climate change is pollution, producing a lot of greenhouse gases that trap heat and warm up the earth. The increase in greenhouse gases is from human activities of burning fossil fuels, deforestation, dumping waste in landfill, and agriculture.

Seeing how human activity is affecting the earth, the UN has set up The Intergovernmental Panel on Climate Change (IPCC) to research further the effect of climate change due to human activity and record evidence of climate change.

Evidence for Climate Change types

Evidence for climate change can be found in recording the environment through scientific instruments over the years, but also by reading natural sources that record how the climate was and comparing it with how it is changing now. These records show changes in temperature, weather, and landscapes. Let's look at the different types of evidence.

Thermometer readings

By comparing present thermometer readings with the past, it is obvious to see that the Earth's temperature is rising. There has been a 1 degree Celsius in rise average surface air temperature since the year 1900. There are also records that 2016 and 2022 are the warmest years on record.

Earlier spring

There have been signs of a seasonal shift, where spring arrives earlier and winter is less cold. This has had an effect on migrating, nesting, and hibernating wildlife.

Glacier retreat

The increase in rising temperature has caused the glaciers to melt and retreat, there is also an increase in sea ice melting in the Arctic. This has been recorded through photography in the past 50 to 100 years where there has been evidence of melted glaciers.

Fig. 1 - Glacier retreating in Svalbard, Norway

Arctic sea ice melting

The sea ice in the Arctic Ocean has been melting more in the summer than refreezing in the winter due to global warming and leading to the decline of Arctic sea ice. Arctic sea ice helps maintain the low temperatures and has an albedo effect on the climate. This means that declining Arctic sea ice leads to increasing ocean heat.

Ice cores

Ice cores are samples of ice removed from an ice sheet or a glacier, many of them are taken from Antarctica and Greenland. From the ice cores, scientists are able to read past atmospheric gas concentrations. The ice core is made from many layers of snow, which traps air in the ice. So from this, they can read the temperature of each year from 400,000 years ago. By comparing the temperatures from 400,000 years ago with the temperatures in the last decade, it is clear evidence that there has been a rapid increase in temperatures.

Sea level rising

The global average sea level has risen 20 centimetres in the last century and in the past two decades has doubled compared to the last century. It is still accelerating every year.

The ocean getting warmer

The temperature of the top 100 meters of the ocean has risen by 0.33 degrees Celcius since 1969. The ocean absorbs a lot of the increased heat with 90% of the earth's extra energy being stored there. This can affect marine ecosystems such as coral reefs and fisheries.

Air temperature rising over the ocean

The air above the ocean is also warming up just like the land and the ocean. This leads to more evaporation and more water vapour in the air. The water vapour can warm up the air and also cause heavy precipitation and fuel potential hurricanes.

Ocean acidification

The increase in acidity in the ocean has risen by 30% since the industrial revolution. The increase in carbon dioxide from human emissions is being absorbed by the ocean which leads to acidification.

Evidence for Climate Change facts

Although it is confusing and frightening to have to face the reality of climate change, there are facts that back up and are evidence for climate change.

• There is the most CO2 in the air in the past two million years.
• 1.2 trillion tonnes of ice are melting each year. As a reference, a combination of all human-made things is 1.1 trillion tonnes.
• In 2019, 302.4 billion work hours have been lost through being too hot to work.
• Severe hot weather events used to happen on average once every 10 years between 1850 and 1900 but now likely occur 2.8 times every 10 years.
• Heavy rains and floods have quadrupled since the 1980s and doubled since 2004.

Evidence for Climate Change map

Maps are a great tool to track evidence for climate change as they work on a global scale which can show the magnitude of the effects of climate change. Climate maps are particularly useful as they can show the various climates of the earth such as temperature and weather.

Fig. 2 - Change in average temperature over 50 years

One of the effects of climate change has been global warming. Thermometer readings of global temperatures were recorded from around the 1850s. In the past, there have been incidents of warming and cooling such as Medieval Climate Anomaly and Little Ice Age, however, compared to the historical events, the rapid rise in temperatures and concentration of carbon dioxide is something that the earth hasn't experienced before.

Fig. 3 - Global glacier mass balance map

Another indicator of climate change is the change in glacier thickness. The map shows the annual thinning of 173 glaciers, which were measured 5 times between 1970 till 2004. The larger circles represent the larger changes and show the areas which are experiencing glacier retreat. With 83% of the surveyed glaciers retreating, it is seen as an effect of global warming.

Evidence for Climate Change development

The latest IPCC climate reports predict that the negative impacts of climate change are developing faster than predicted 10 years ago. This report shows the urgency of the situation as climate change develops. There are many that are vulnerable to climate change with between 3.3 billion and 3.6 billion people's places they call home at risk. This is 40 % of the earth's population. It is also said that the changes that the global temperature rise is causing may become irreversible when the rise in temperature reaches 1.5 degrees celsius above. The report may be alarming however it is important to build predictions based on facts and evidence to help governments to understand the reality of this situation and act toward changing the way human activity is affecting the climate.