At the 26th UN Climate Change Conference (COP26), which ended on the 13th, a true scene was made.
This is because the foreign minister of Tuvalu, an island nation in the South Pacific, gave an underwater speech while kneeling.
Tuvalu has an average elevation of 2 to 4 meters above sea level, and the country is increasingly submerged with sea level rise every year.
If sea levels continue to rise according to current trends, it is highly likely that all of Tuvalu will disappear into the sea within the next 50 years.
In this speech, Foreign Minister Simon Kope emphasized that "the suffering Tuvalu is experiencing due to climate change will ultimately be the same for all mankind."
"Climate change and sea level rise are deadly and existential threats to Tuvalu and low-lying atoll countries. We are sinking, but so is everyone else."
Some countries are desperate enough to have their ministers dive into the water, but most countries aren't like this yet.
But that does not mean that countries around the world, including us, are far from the consequences of climate change.
Let's take a look at the current situation in Korea, where the fairly cold air is on the rise, signaling winter.
This year, the clothes for autumn in the closet were of no use.
In fact, in October, the national average temperature was 15.1℃, which was about 1℃ higher than normal, and in early October, the maximum temperature soared to 26.5℃.
This is the highest record since 1973*.
The Korea Meteorological Administration defines the start of autumn as the first day when the average daily temperature falls below 20°C and does not rise again.
The Korea Meteorological Administration will accurately announce the end of this fall through post-mortem analysis, but now that the cold wind is blowing vividly, everyone would have felt that this fall was short.
It's not just this year's situation that talks about climate change.
According to seasonal statistical data analyzed by the Korea Meteorological Administration for over 100 years, the actual start date and length of fall are getting shorter.
I am not talking about the fact that shorter autumn can cause great damage to mankind, but I want to say that you can feel climate change indirectly at this point in the current Korean Peninsula.
(Source: Korea Meteorological Administration)
* 1973 is the period when the weather observation network was expanded to all parts of Korea.
Can climate change be prevented?
In the Paris Agreement, mankind set the marginal line for temperature rise at 1.5°C. But it won't be easy. Climate Action Tracker, an international environmental group, predicted that the global temperature would rise by 2.4°C in 2100 compared to pre-industrial levels if each country's greenhouse gas reductions set out at the general meeting of the climate change convention were followed. This is 0.9°C higher than our target. In the scenario where the temperature rises the most among the group's scenarios, the global temperature rose to a whopping 2.7°C in 2100. The group estimated that if it were the current state, greenhouse gases equivalent to twice the greenhouse gas emission required for the target increase would be emitted by 2030. Experts analyzed that in order to achieve the target of 1.5℃, greenhouse gas reduction should be reduced by at least 45% compared to 2010.
If so, will all the problems be solved if each country succeeds in reducing greenhouse gas emissions and matches the rise of 1.5℃, leaving behind economic and political problems? Unfortunately, it is not. Since the Industrial Revolution, the carbon dioxide concentration has risen rapidly and the temperature has risen, but there is still a lot of room for this temperature rise. This is because the Earth has not yet fully responded to the increased carbon dioxide. For example, when carbon dioxide concentrations in the past increase, heat accumulated in the ocean can be released later, causing a rise in temperature. Solar energy on the Korean Peninsula is strongest in summer, but it is easy to understand when you consider that the sea temperature is highest around September in the slow-responsive ocean.
So, what if the carbon dioxide concentration was lowered like before industrialization, instead of at 1.5°C?
A research team led by Professor Soon-il Ahn of Yonsei University tried to turn back the clock of carbon dioxide through a climate model experiment*.
The carbon dioxide concentration was reduced from the current concentration (410ppm) to the concentration before the industrial revolution (280ppm).
However, it was confirmed that the earth's temperature did not return to the pre-industrial temperature, and temperatures higher than this persisted for hundreds of years.
The main reason for maintaining high temperatures is the Atlantic meridional overturning circulation (AMOC), which transfers heat from the equator to the poles.
The Atlantic Ocean circulation is currently weakened by the mixing of freshwater with the melting of sea ice and land ice due to global warming.
That is, the heat of the ocean is not going from the equator to the North Atlantic.
For this reason, the Northern Hemisphere temperature has increased by 2-3 °C over the past 100 years, but the temperature change in the North Atlantic has been minimal.
Conversely, when the carbon dioxide concentration is lowered as in the experiment, this cycle is revived, but the problem is that when the cycle is restored, it overshoots to a greater extent than the original strength.
The strong circulation supplies more heat to the northern hemisphere, which in turn causes higher temperatures than in the past.
Earth system, has crossed a line that should not be crossed?
Even if the carbon dioxide concentration is reduced, we have to live at a higher temperature than before industrialization for hundreds of years. So how high is the temperature? Experts say about 1.5℃~2℃. How dangerous this condition can be because no one can predict the future. However, as we set 1.5~2℃ as the marginal line, I hope that it simply means that the climate will last a long time at the limit that can prevent dangerous shocks.
However, climatologists suggest another possibility. By 2050, when we aim to be carbon-neutral, overshooting, in which the temperature rises significantly, will occur. If this happens, the global temperature will rise more than the currently predicted 1.5~2℃ rise, and higher temperatures may appear. Although this prediction is a prediction with high uncertainty at the moment, experts say that the possibility itself cannot be ruled out.
Climatologists warn that if the current climate system breaks down and crosses a line (critical point), big changes will occur everywhere. Because the change is so rapid, it will entail major changes and may lead to new climates that we have never known about. Climatologists are now watching these major changes as Arctic sea ice and Greenland disappearance, coral reef extinction, tundra disappearance, a reversal of large-scale ocean circulation in the Atlantic Ocean, and deforestation of the Amazon rainforest. Unfortunately, the disappearance of coral reefs and the disappearance of sea ice in the summer arctic have already crossed the line, and even if the Paris Agreement succeeds, it is predicted that major changes will not be prevented. Because the Earth system is organically connected, once such a major change occurs, it can appear like dominoes anywhere. That is why we must try not to cross this line.
A country that participated in the Conference of the Parties to the Climate Change Convention mentioned that its efforts on carbon emissions were inevitably negligible due to economic sanctions.
Climate change is the most important and urgent problem that mankind must solve.
Naturally, I think that solving this problem should be a priority over anything right now.
I hope that resolving this issue will be the top priority for both those who are sanctioned and those who are being sanctioned.
<References>
Soon-Il An, Jongsoo Shin, Sang-Wook Yeh, Seok-Woo Son, Jong-Seong Kug, Seung-Ki Min, Hyo-Jeong Kim, "Global Cooling Hiatus Driven by an AMOC Overshoot in a Carbon Dioxide Removal Scenario", Earth's Future (2021), doi.org/10.1029/2021EF002165