Limit global temperature rise to below 1.5˚C

 

 

By Science Columnist Ho-Gwan Ko

 

These days, we hear the word “record-breaking” quite often, as in “record-breaking heat wave,” “record-breaking cold wave,” and “record-breaking flood.” More specifically, you can easily hear news about “the hottest summer in 00 years.” Then, how fast is climate changing breaking all the records?

Humans have contributed to global warming since they started burning wood or coal for heating and cooking. However, the impact on global warming over the past 100 years is far greater than the 10,000 years for which humans have lived civilized lives. It’s difficult to know the exact temperatures in the past when there were no thermometers. Compared to the second half of the 19th century, however, global temperatures in the last decade were about 0.9°C higher.

The temperatures have risen more rapidly since the 1960s, and they are still rising by 0.2°C every 10 years. Unless we make a lot of effort, it will get worse rather than better. One or two degrees Celsius may seem insignificant, but the climate change we’re experiencing now starts from such seemingly small changes.

As temperatures rise, the Earth undergoes a number of changes. Arctic sea ice reaches its annual minimum each September, and we can see the changes by measuring and comparing the thickness of the ice. According to satellite observations, Arctic sea ice has continuously decreased since the 1980s. In 2012, it recorded the lowest since observation started. It’s reducing by about 13 percent every 10 years.

Ocean temperatures are also rising steadily. We often hear from the news media that different types of fish are caught or there is a sudden surge in jellyfish due to the increase in ocean temperatures. According to the National Oceanic and Atmospheric Administration (NOAA), the average sea surface temperature has risen 0.13°C every 10 years over the past 100 years.

When the ocean temperature rises, sea levels also increase. This is because the amount of seawater increases due to melting glaciers in the Arctic and Antarctic, with the volume of water expanding as the temperature increases. Over the past 100 years, sea levels have risen by about 180 mm, and they are still rising by 3.3 mm every year.

At the 48th Session of the Intergovernmental Panel on Climate Change (IPCC) held in 2018, climate scientists announced that we should prevent the global temperature from rising an additional 1.5°C above pre-industrial levels. The previous agreement was to limit it to 2°C, but it was considered no longer sufficient.

If we’re able to limit the temperature rise to 1.5°C by 2100, the sea level will be 10 cm lower than compared to the 2°C scenario. Although it seems like a negligible difference, it could get as many as 10 million people out of the crisis. While a 2°C rise would make more than 99% of coral reefs disappear, a 1.5°C increase may lower the number to 70-90%. The probability of Arctic sea ice melting and disappearing in summer also decreases from once every 10 years to once every 100 years.

To limit the temperature rise to below 1.5°C, carbon emissions must be zero by 2050. This means that there should be no man-made carbon dioxide at all. Transportation modes such as personal vehicles must be run on electricity, and carbon dioxide generated from power plants or factories must be collected and trapped in designated storage so that it does not flow into the air.

It may not seem easy, but it must be done. If climate change continues at its current pace, it’s highly likely that there is no future for mankind. If we can't stop it as quickly as possible, climate change will create a vicious cycle threatening our lives. This is because climate change leads to more frequent wildfires releasing more carbon dioxide, makes the gas dissolved in the ocean escape, and releases methane gas trapped in permafrost, accelerating global warming. If this happens, we need to take more aggressive measures to remove carbon dioxide using technologies including artificial photosynthesis.

 

Some scientists have already warned that we may have passed the tipping point for climate change. It’s like a death sentence for mankind. However, we can't just give up. Humans have made it through multiple crises. It’s true that climate change is the most difficult issue we have ever had, but it may not be too late if everyone works together.