Greenhouse gas emissions over the next few years will determine the rate of global warming, sea level rise and the magnitude of natural disasters in the next century and in the next millennium

The world is warming as a result of human activity, and mainly due to the greenhouse gases that are emitted to the atmosphere when we burn fossil fuels. The Intergovernmental Panel On Climate Change (IPCC) has already determined that there can hardly be any doubt about the matter, in light of the myriad of accurate measurements, observations, scientific theories and calculations published in thousands of scientific articles by researchers around the world.

The amount of greenhouse gases we emit is growing, and the Earth’s surface temperature is rising along with this increase, as does the frequency and magnitude of natural disasters, such as heat waves, floods, hurricanes and periods of drought. The consequences of global warming are already being felt today and are expected to seriously aggravate by the end of the century. How bad will it be? This will depend mainly on the amount of greenhouse gases we will continue to emit in the near future.

The choice we face is between ‘not good’ and ‘truly disastrous’. The IPCC panel has estimated that if we reduce the emission of these gases and adhere to the decisions of the Paris Agreement, we will still experience a severe heatwave every six years, of the kind that used to occur only once every fifty years. If we continue to increase greenhouse gas emissions at the current rate, we will experience comparable heatwaves almost every year, and these are expected to get more severe and warmer by three degrees Celsius on average.

According to these forecasts, under the optimistic scenario, the region of the Middle East, for example, will experience ‘once in a decade’ droughts every five years. Under the pessimistic scenario, these droughts will occur every two and a half years on average, and will become more severe. Such changes will have profound ramifications on quality of life, on the availability of food and water, on global geopolitical stability, as well as on wildlife and ecosystems. According to United Nations Secretary-General António Guterres, “If all governments — especially G20 governments — do not stand up and lead efforts against the climate crisis, we are headed for terrible human suffering”. 

To make matters worse, the effects of the greenhouse gases emitted today will not dissipate within the next century. Unless we take sufficient and adequate measures to reduce greenhouse gas emissions today, their presence in the atmosphere will continue to heat up the planet and cause damage for centuries to come.

קרחון נשבר באנטרקטיקה. צילום: Bernhard Staehli Shutterstock
The choice we face is between ‘not good’ and ‘truly disastrous’. A glacier breaking in Antarctica | Photo: Bernhard Staehli Shutterstock

Carbon is Forever

The lifetime of a greenhouse gas in the atmosphere, or, in other words, the average time it lingers in the atmosphere after reaching it, depends on the type of gas. Methane, for example, is considered a comparatively short-lived gas. After its emission from a cow’s digestive system, an offshore drilling rig, or from another source, it remains in the atmosphere and absorbs radiation for about 12 years on average. Therefore, if we reduce our methane emissions today, we will see results in the near future.

The effects of carbon dioxide are much more long lasting. According to oceanographer David Archer from the University of Chicago “The lifetime of fossil fuel CO2 in the atmosphere is a few centuries, plus 25 percent that lasts essentially forever. The next time you fill your tank, reflect upon this”

The carbon cycle consists of a number of processes, of which only the slow ones completely remove carbon from the atmosphere. A molecule of atmospheric carbon dioxide will dissolve into seawater within a short five years on average, but will also get released back into the atmosphere at a similar rate. Due to the rising concentration of carbon dioxide in the atmosphere, the oceans today absorb more carbon than they emit, with the upper layer of water absorbing about a quarter of the annual amount of carbon dioxide emitted by humanity. However, the upper layer of water can absorb only a limited amount of carbon dioxide, and it hardly ever mixes with the deeper waters. 

Over the next few centuries, dissolved carbon dioxide will slowly seep into the depths of the ocean, while ocean currents will bring up deeper water to absorb more carbon. Over thousands of years, carbon dioxide dissolved in the deep sea will react with calcareous deposits at the ocean floor, thus allowing more carbon dioxide to dissolve in the ocean. This process works in the opposite direction to the formation of the calcareous sediments from skeletons of marine organisms, such as shells and corals. However, this process too is limited, and some of the carbon dioxide we emit will be removed from the air only when it dissolves in rainwater, thereby increasing its acidity and allowing the resulting solution to react with rocks and form new minerals. The timescale of this process is hundreds of thousands of years, a time scope similar to the period of time that has passed since the human race, Homo sapiens, first appeared on the evolutionary stage.

Model simulation describing the absorption of carbon from the atmosphere over 40, 000 years, after large carbon dioxide emissions from fossil fuels combustion | Nature Climate Change (Nat. Clim. Chang.), reproduced from The Long Thaw.

A small fraction of the carbon dioxide that we emit will be absorbed through other long processes. Trees, microscopic algae and other organisms also absorb vast amounts of carbon dioxide, but carbon dioxide is released back into the atmosphere with each breath a living creature exhales as well as through the decay process of each creature that dies. The forests and lands around the world absorb about a third of the carbon dioxide we emit, but this process is limited, and unless we preserve them, they will emit the carbon back into the atmosphere.

Some of the carbon found in dead animal matter gets buried in the ground or in the ocean floor and is not released back into the atmosphere. Instead, it turns into rock or fossil fuels, through processes that span millions of years. Volcanic activity and tectonic processes that cause rocks to melt and become hot magma and gas, release some of the carbon back into the atmosphere. This process can change the composition of the atmosphere over millions of years. 

However, if natural processes cannot quickly remove carbon dioxide from the atmosphere, maybe we can do it ourselves? Although in the current century our ability to remove carbon dioxide from the atmosphere artificially will likely remain quite minimal, it may become much more significant in the more distant future. Until then, this costly technology could make a limited contribution to carbon removal, and it could be applied to offset industrial emissions that are too difficult or exceptionally expensive to eliminate.

Relative to the scale of a human lifetime, carbon dioxide will remain in the atmosphere forever, and as long as it stays there it will continue to warm planet Earth and change the acidity of the ocean. According to a 2008 study, even if greenhouse gas emissions are eliminated entirely, atmospheric temperatures will continue to rise for several decades, and may not decrease appreciably for several centuries at least. Another study has shown that it will take nearly 12 thousand years for Earth's climate to cool by as little as one degree Celsius.

Sea Level: The Great Tide

About 90 percent of the heat that was gained by the Earth's climate system has so far been absorbed by the ocean, and this amount is expected to increase by 2-8 times by the end of the century, depending on the extent of greenhouse gases that we will emit until then.  The warming of seawater leads to marine heatwaves - extreme climatic oceanic events that can have devastating impacts on marine ecosystems, lead to decrease in the concentration of oxygen dissolved in the water, as well as in other changes. In addition to the severe damage inflicted on marine ecosystems, such as coral reefs, water warming also leads to expanding water volume, and so far this phenomenon has been responsible for about half of the increase in sea levels over the last fifty years. Ocean warming is expected to continue for hundreds to thousands of years, during which heat will gradually penetrate into the depths of the oceans.

Glacier melting is also expected to continue for hundreds if not thousands of years, as the world is getting warmer. Extensive parts of Greenland and West Antarctica are at risk of thawing, which would exacerbate and accelerate the rise in global sea levels. Unless we reduce greenhouse gas emissions drastically, it is very likely that we will completely and irreversibly lose these frozen regions, which is likely to result in a rise of several meters in seawater levels.


המסת קרחונים (גרינלנד) צילום: Maria-José Viñas NASA
Melting glaciers (Greenland) | Photo: Maria-José Viñas NASA

Over the last hundred years, sea levels have risen by only about 20 cm on average, but the rate of rise is increasing. Today, sea levels are rising by 3.7 mm per year, and by the end of the century they are expected to rise by another 30 cm to one meter on average, flooding areas in which hundreds of millions of people live today, rendering them uninhabitable and endangering entire island nations. In addition to flooding due to tidal waves, the rise of sea levels will exacerbate the consequences of natural disasters. Storm waves will penetrate deeper inland, endangering lives, increasing salinity levels of drinking water supplies and damaging infrastructure. These risks will increase with the escalation of storms and hurricanes in an era of a warming climate.

It is also possible that the rise in sea levels will become faster and more significant already in the coming century: we still do not adequately understand the complex dynamics of the loss of terrestrial ice sheets, especially in the context of glacier motion towars the oceans and the detachment of floating ice shelves that are still connected to the frozen continents. Increased greenhouse gas emissions increase the risk of unexpected detachment of ice shelves.

Sea levels are not rising uniformly all over the world. The degree of sea level rise in each area depends on the specific marine characteristics, such as marine currents, as well as the land characteristics, large parts of which may sink or rise, for example as a result of the melting of massive glaciers that once covered entire areas during the last ice age. Thus, while sea levels are dropping along some parts of Canada’s coastline, in the state of Louisiana in the United States, sea levels have already risen by about 60 cm since 1950, and today it is losing an area equivalent to a tennis court every few minutes.

​A film produced as part of a project designed to raise awareness to the climate crisis:

A Turning Point

Much like the glaciers, many systems in the world react slowly to temperature changes, but once these cross a certain threshold, their consequences will be rapid and irreversible. This may result, for example, in loss of the Gulf Stream that warms Europe, or of the Amazon tropical rainforests that serve both as storage for massive amounts of carbon as well as a conservation haven for an incredible array of biodiversity. It may also result in the thawing of permafrost, which will lead to the release of more greenhouse gases. The likelihood of these scenarios materializing in the coming century is relatively low, but they may indeed occur in the more distant future. Real concern exists regarding the possibility that the Amazon rainforests will be lost during the next one hundred years. Excessive emission of greenhouse gasses will increase the risk of these dramatic changes occurring, and will accelerate them.

Climate change will affect not only us humans, but also the rest of the living things  on Earth. The shift in climate regions is likely to bring upon migration of species and of entire ecosystems across the globe, and consequently result in the extinction of those who cannot follow the changing climate fast enough, or of those who will be left with no suitable or accessible habitat. Damage to ecosystems can also affect climate, for example by leading to fixation of smaller amounts of carbon, or by extending the extent of desertification.

ועימה עולות גם טמפרטורת פני כדור הארץ והשכיחות והעוצמה של אסונות טבע. צילום: TR STOK Shutterstock
The amount of greenhouse gases we emit is increasing, and along with it, global temperatures are rising and the frequency and magnitude of natural disasters are increasing | Photo: TR STOK, Shutterstock

Ambitious Goals Are Required

The climate crisis is already here, and it is expected to worsen for many years to come. The rate of climate change and its severity will depend on the amount of gases we emit in the near future. Every ton of carbon dioxide matters, and ambitious policy goals backed up by action are probably the most important tool for reducing emissions.

In order to mitigate the crisis and meet the goals delineated in the Paris Agreement, global greenhouse gas emissions must be reduced within a decade by at least 45 percent relative to 2010, as well as completely balanced out by 2050. However, analysis of current commitments of the world’s countries shows that the world is very far from meeting these goals.

Although many countries have commited to the required reduction, few have passed stringent and binding climate laws and many do nor have an authorized or funded national plan to achieve this. China, who is responsible for more than a quarter of global emissions, has committed to zero emissions by 2060, but in the next decade its emissions are expected to continue to rise.

The mission of the UN Climate Change Conference in Glasgow (COP26) is to ensure that the world meets the goals of the Paris Agreement. In order to do so, countries are required to set goals more ambitious than the ones they have set in the past and to promote more collaboration. Immediate goals include accelerating the transition from coal to less polluting fuels, stopping deforestation, implementing fast transition to electric transportation and investing considerable funding in renewable energy. According to the UN secretary-general António Guterres, “Either we stop [our addiction to fossil fuels] - or it stops us”. In addition, the conference seeks to protect and rehabilitate ecosystems. It is also supposed to encourage wealthy countries to meet the financial commitments of the Paris Agreement, which consisted of the transfer of about one hundred billion dollars a year to developing countries in order to help them to reduce their emissions and to prepare for the climate crisis.

English television broadcaster and natural historian, David Attenborough said at the Global Climate Change Conference (COP26) that “We are, after all, the greatest problem solvers to have ever existed on Earth. If working apart, we are a force powerful enough to destabilize our planet, surely working together, we are powerful enough to save it. In my lifetime, I've witnessed a terrible decline. In your lifetimes, you could and should witness a wonderful recovery.” 

Taken from Sir David Attenborough’s speech at the Climate Conference in Glasgow.