Glaciers are melting, coral reefs are bleaching, trees are drying up and the Gulf Stream current weakens. These are all signs that global warming is slowly leaving its mark and throwing nature out of balance. So far, the consequences for people, animals and plants are still manageable. But if the temperatures continue to rise, we will reach critical points that will significantly accelerate climate change.
The Potsdam Institute for Climate Impact Research describes the climate change problem with a metaphor. If you push a coffee cup a little over the edge of the desk, nothing happens at first. It becomes problematic once it reaches a critical point where it tips and falls.
The coffee cup is synonymous with the climate. So far it’s still pretty stable. However, an international team of researchers has identified some climate change tipping points that could bring it out of balance.
1. Permafrost thaws
The Arctic permafrost in Siberia and North America are a globally important carbon reservoir. Scientists estimate that the frozen ground has stored between 1,300 and 1,600 billion tons of carbon. That would probably be 50 percent of the total carbon stored in the soil worldwide. It comes from animal and plant remains that were stored there during and since the last Ice Age.
American scientists showed that the permafrost areas warmed up by four degrees between 1990 and 2016. When the permafrost thaws, the trapped carbon breaks down and is released. Researchers estimate that around 15 percent of the bound carbon could be released by 2100. These quantities could significantly accelerate global warming.
2. Less sea ice at the poles
The area-wide sea ice has an important function for the earth’s climate. It cools the planet all year round. The decisive point here is the so-called ice-albedo feedback. Currently, ice and snow still deflect sun rays back into space. If the ice melts due to global warming, it can no longer deflect radiation and the earth will continue to heat up.
As a result of this effect, climate change will advance twice as fast in the northern regions. According to a report by the IPCC, if the temperature would be only 2 degrees higher, ice in the Arctic Ocean would thaw every summer. That basically means that the region would be ice-free.
New study results confirm that the tipping points exist in West and East Antarctica. The researchers conclude that the sea level could rise more than six meters with a warming of four degrees.
The ice sheet on Greenland is also slowly melting. At the moment, the surface of the glacier is located in cool layers of air at an altitude of 3000 meters. However, as they slowly melt, they sink – and get into warmer layers of air. The melting effect intensifies itself.
3. Deforestation and fires in the primeval forests
The Amazon rainforest as well as the boreal coniferous forests in Canada and Siberia suffer from periods of drought, fires and ongoing deforestation. Each tree stores large amounts of carbon, which is released into the atmosphere if the tree burns down.
In addition to CO2 emissions, deforestation also has an impact on regional weather. The fewer trees a rainforest has, the lower the amount of precipitation on site. Trees evaporate water from their leaves. If there are no trees, there is less moisture in the air and there is less rain. As a result the soil becomes drier and the rainforest loses its resilience. Even today, parts of the tree population are not able to cope with the new climatic conditions and are dying, as some researchers report. This in turn could result in the transformation into a drought-adapted seasonal forest or a grassy landscape. While bush and grasslands could displace boreal coniferous forests.
If forest destruction continues, the Amazon forest would be transformed from a carbon sink into a carbon source by 2035, predicts a British study. In other words, it would release more carbon than it absorbs.
That would be fatal, because around a quarter of the global carbon cycle takes place here. The Amazon rainforest is considered the green lung of earth for a reason. Scientists estimate that living and dead plant material in the Amazon region alone stores 80 to 120 billion tons of carbon. That is more than has been released around the world in the past three years. If this stored carbon were to enter the atmosphere, this would have not only regional but also global consequences for the climate.
4. Methane hydrates on the seafloor
Methane hydrates are basically methane enclosed in ice. It is found in oceans and seas all over the world. Many methane hydrates have trapped sand or rocks and have sunk to the seafloor.
With the increasing warming of the oceans, there is a risk that the ice will melt and the methane will be released. Methane has a significantly more negative effect on global warming than CO2.
5. Ocean carbon uptake
So far the oceans had a tremendous effect on climate change. Around 40 percent of anthropogenic CO2 emissions were stored in the oceans, mainly in algae. These normally absorb the CO2, grow, die and take the bound carbon with them into the deep sea. But due to the increasing temperatures, the oxygen content of the sea decreases, so that fewer algae grow. As a result, the ocean absorbs significantly less CO2.
6. The Gulf Stream current is slowing down
The Gulf Stream is a strong current in the Atlantic Ocean. It conducts warm water along the surface of the sea from south to north, where it gives off heat to the cool air. This is how the North Atlantic area is heated all the way to Europe. Without the Gulf Stream it would be much colder in northern Western Europe, and winters would be similar to those in Siberia.
However, the water in the sub polar North Atlantic has cooled noticeably since the middle of the 20th century. The possible cause: the weakening of the Gulf Stream current. An international study came to the conclusion that the current has already decreased in speed by up to 15 percent. Climate researchers suspect that increased freshwater supply due to rain and ice melting could be responsible for this. Fresh water does not sink because it is lighter than salt water. This could hinder the Atlantic circulation, which is powered by the sinking of cold water and the rising of warm water.
Global warming could make the Gulf Stream even slower. We can only estimate by how much based on models. The range is from a few to 50 percent this century. Should the Gulf Stream stop circulating at some point, the consequences would be severe. For example, Europe would experience more extreme weather. Important ecosystems in the North Atlantic could collapse and the sea level on the US coast could rise by up to one meter.
The consequences of climate change would be irreversible
Any such tipping point could trigger uncontrollable, self-reinforcing processes in important ecosystems. Permafrost soils, methane hydrates and forests, for example, would further intensify the global rise in temperature. A climate chain reaction is then possible. According to researchers, these tilting elements could act like a series of dominoes. If one of them is tilted, this element pushes the earth towards another tipping point. Then, it could be very difficult or even impossible to stop this chain reaction.
Crop failures, hunger and disease
If the earth warms up by several degrees, a massive rise in sea level lasting thousands of years would be one possible consequence. This will also lead to an extreme heat around the equator. Researchers predict crop failures, hunger, spread of diseases, mass migration and international conflicts that would lead to the global destabilization. In addition, important ecosystems for animals and plants would be destroyed by temperature changes and extreme weather conditions.
So far these are only forecasts
It is unclear whether the tipping points will really occur at some point. For climate research, however, it was important to define them. With the help of climate models it is possible to calculate various climate change scenarios. This gives scientists an orientation in which directions their future research focus should be. However, it is also clear that climate models can be wrong. It is common to adjust them every few years. Depending on how the situation develops. As for the tipping points, the prognosis of reaching a critical point can change in the next few years.
Critical areas must be kept in mind
Researchers maintain that it is important to understand that the consequences of crossing climate change tipping points would be catastrophic for humanity.
By defining the tipping points, climate researchers now have the critical areas in view. These are the permafrost soils, rainforests, sea ice, glaciers, methane hydrates, Gulf Stream current and oceans. According to the researchers, physical systems such as ice sheets and ocean circulation, have highly reliable basic models and simulations. Therefore, statements about tipping points are very relevant, even if there are uncertainties and different expert opinions. For biological and ecological systems such as the Amazon rainforest or boreal coniferous forests, the uncertainties are greater.
Tilting factors could destabilize each other
Last year, a much-cited study on the “Hothouse Earth” triggered a discussion whether it was even possible to limit global warming to two degrees. Precisely because these feedback processes exist at the tipping points. A preliminary research also indicates that the tilting factors can destabilize each other through their versatile interactions.
Curb global warming
The current prognosis is that the tipping points will cause irreversible climate damage once the earth has warmed over two degrees. So if we manage to keep global warming below 1.5 degrees, we could prevent the chain reaction with a security buffer. To do this, we would have to reduce our global CO2 emissions by around 8.5 percent every year. The IPCC calculated it in a special report in November 2018.
But despite the agreed climate targets, global greenhouse gas emissions are still far too high. Fossil fuels play a large part in this. In order for us to achieve the 1.5 degree target, it is not enough for individual countries to reduce their emissions. In the worst case, these will only shift from one state to the next. It is therefore important that all countries pull together so that we do reach dangerous tipping points.