Paris Agreement? Forget 1.5 degrees, we’d be lucky to keep global warming below 2 °C

Figure 1: Fossil-based carbon dioxide (CO₂) emissions in billions of tons since 1750. It can be seen that emissions were very low prior to the industrial revolution. Until the mid-20^th century, emissions growth was relatively slow. In 1950, the world emitted approx. 6 billion tons of CO₂. By 1990, this had almost quadrupled to 22 billion tons. Emissions continue to grow rapidly, with over 34-35 billion tons now emitted annually. Source: Own work based on Our World in Data billions of tons China; United States; India; Russia; Germany; Brazil; UK; France

Atmospheric concentrations of greenhouse gases* reflect the balance between natural processes and anthropogenic emissions, sources and sinks. Increasing levels of greenhouse gases in the atmosphere are a major driver of contemporary climate change.

Throughout the last 800,000 years, there certainly has not been as much carbon dioxide in the atmosphere as there is now. The ever more severe greenhouse effect is causing average global temperatures to rise unstoppably, with the rate of increase since 1880 standing at approximately 1 °C

Figure 2: Atmospheric levels of carbon dioxide (CO₂) over the past 800,000 years. A strong correlation can be observed between change in temperature and the concentration of carbon dioxide. Sources: Snyder et al. 2016; Stips et al., 2016; NOAA; Copernicus

About four decades ago, the Earth entered a period of intense warming. This is well proven by the fact that the ten warmest years since records began have all been since 1980, with eight of these observed between 2010 and 2033.

According to the 2023 dataset disclosed by the World Meteorological Organization (WMO), the global average temperature in the year 2022 was about 1.15 (±0.12) °C above the pre-industrial average (1850-1900).

Although the increase in temperatures has been ever more pronounced, the growth temporarily decelerated in 2021 and 2022. This was due to a strong La Niña event in the Pacific Ocean, which reduced global average temperatures by 0.3-0.4 °C. However, the intensifying El Niño expected from the second half of 2023 is believed by climatologists to lead to a sudden spike in temperatures, meaning that the year 2024 could be in the record-breaking range.

The rise in temperatures is significant not only at global level but also in our region, Europe. Aggregate data recorded by weather stations across the world suggest that 2022 was the fifth hottest year on record globally, the second hottest in Europe and the third hottest in Hungary.

According to the WMO report ‘State of the Global Climate in 2022’, extreme heat waves, droughts and devastating floods could affect millions of people and cost billions of dollars in 2022. The pace of sea level rise has doubled since 1993, rising by nearly 10 mm since January 2020 and reaching a new record high in 2022. The last two and a half years alone account for ten percent of the total sea level rise since the start of satellite-based measurements nearly forty years ago.

The melting of polar ice has accelerated in recent years, with increased melting observed not only in the lower latitudes of the Northern Hemisphere but also in Antarctica. During summers, Greenland has already experienced an increase in the number of rainy days from zero to two, and the island has seen a positive temperature anomaly in the range of 15-20 °C in almost every year over the past two decades.

In 2022, historic heat waves and droughts devastated much of the Northern Hemisphere; floods, rockslides and landslides were observed in the Mediterranean in August; and three tornadoes in four days were detected in Croatia. What is most worrying, however, is that the temperature of the Mediterranean Sea exceeded the average by 4-5 °C. An Atlantic hurricane formed 2,000 kilometers further north than usual and a bomb cyclone (storm cyclone) was observed in North America over Christmas. The Southern Hemisphere also saw a wealth of extreme weather phenomena, with unprecedented floods in Australia, the Andes recording record-low temperatures for months and Antarctica reaching its lowest ice coverage ever.

If we are to follow current climate policies, a temperature growth of over 2 °C above pre-industrial levels is expected by the end of the century. Such an increase will not only induce further extremes but is also a far cry from Paris Agreement targets. (It should be noted here that any natural phenomenon has the potential to accelerate or slow down this process; there is even a very slim chance that it could be reversed naturally.)

What does this translate into?

According to the IPCC’s AR6 report, the likelihood of temporarily exceeding the 1.5 °C limit set out by the Paris Agreement is increasing over time and temperature growth is expected to rise permanently above this threshold in the 2030s. Because the period certain greenhouse gases can linger in the atmosphere and exacerbate climate change ranges from 50-200 years for carbon dioxide, a few years for methane, several decades for nitrous oxide (responsible for 6 percent of the greenhouse effect) and up to two or three thousand years in the case of exclusively man-made halogenated and fluorinated hydrocarbons, this would happen even if humanity were to significantly reduce its GHG emissions this very day.

Due to its much higher heat storage capacity compared to carbon dioxide, methane is clearly largely to blame for the heavy rise in temperatures in the short term (over a two to three-decade period at most). Methane is the second most important greenhouse gas after carbon dioxide. It is, however, present in the atmosphere in quantities about 200 times smaller and remains within it for only a few years, while carbon dioxide lingers on for up to two centuries. In other words, methane picks up heat quickly but swiftly exits the atmosphere, while carbon dioxide retains less heat decade by decade.

Figure 3: Time to sustained temperature transition above 1.5 °C. According to the linear trend, the tipping point is expected in 2035; IPCC projects it for as early as 2029-2030. Source: Copernicus/CCS

Today’s scientific knowledge suggests that based on current emissions, the global average temperature increase could exceed 2 °C by the mid-21^st century and up to 2.5-2.8 °C by 2080. The most pessimistic scenarios predict that even a 4 °C increase is not out of question. The latter would be seen if GHG emissions continue to rise until 2050 and decline only moderately thereafter.

Despite G20 countries, responsible for 80-82 percent of global emissions, still falling short on commitments, there had been some progress in the years leading up to the war between Russia and Ukraine.

An example for this advancement is the U.S. Inflation Reduction Act, which aims to quadruple clean energy capacity by 2035. In spite of estimates that the Act could reduce the country’s emissions by 40 percent in the running decade, the war and the global economic crisis could cause a spike in U.S. emissions, postponing the commitment until 2040.

In recent years, the European Union has been joined by Switzerland, Iceland and Norway in setting new climate targets, including the Fit for 55 initiative. The new European Climate Agenda has made it a legal obligation to meet the EU’s climate target of reducing community-level emissions by at least 55 percent until 2030. European countries are working on new legislation to meet this target and achieve climate neutrality by 2050. As the energy crisis starting in 2022 will see the reopening of several fossil-fuel power plants, some analysts doubt that the European Union will succeed in cutting emissions by 55 percent until 2030; that being said, the green label for nuclear power is a positive development.

Australia, a country only marginally exposed to the energy crisis, is seeking to achieve a 43 percent reduction of its carbon emissions by 2030 and aims to eliminate them completely by 2050 under a new Climate Change Act, passed by the country’s parliament in 2022.

South Korea and Japan are pursuing similar targets. Unfortunately, serious efforts are yet to be seen from other major emitters, and the increase in GHG emissions by China and India is particularly worrying. China, however, has recently announced its intention of becoming climate neutral by 2060. If the undertaking proves successful, global warming would be reduced by 0.25-0.3 °C.

Figure 4: To meet the Paris targets, global CO₂ emissions must reach net zero to limit global warming. Achieving net zero CO₂ emissions by 2050 will require a reduction of about 1.4 Gt in CO₂ output per annum, mirroring the period during the COVID-19 pandemic. Source: own work based on GCP/IPCC

What would the much-discussed 1.5 and 2 °C mean for the world?

1) Successfully keeping warming just below 1.5 °C. Under the least pessimistic scenario, the climate on Earth would remain close to what we see today, but laced with extremities. Both minimum and maximum temperatures continue to rise. Countries significantly reduce global emissions by 2050, with a slim chance (<5 percent) of a slow cooling period setting on between 2080 and 2100. It would see Western and other developed societies shifting to more sustainable practices, and the focus move from economic growth to overall prosperity. By 2100, the EU is using exclusively clean nuclear and renewable energy and the U.S. has reached 90 percent greening. China becomes climate neutral by 2060. China’s GHG emissions peak around 2025, after which no significant change is seen in emissions for nearly a decade; however, a sharp decline around 2035 could reduce carbon emissions by 20 percent below the peak, followed by a reduction of over 70 percent by 2050. In consequence, renewable and nuclear energy would account for over 80 percent of the country’s power generation after 2050.

Africa could become the continent with the largest solar farms on the planet.

Among the OPEC states, Arab countries are cutting their hydrocarbon production by 90 percent compared to 2010 levels. Investments in education and health are increasing. Levels of inequality are falling.

Although extreme weather will become more frequent, the world will avoid the worst impacts of climate change. Temperatures in Europe could rise by over 2.2-2.8 °C. The continent’s glaciers may retreat by up to 20 percent by the end of the century, threatening drinking water supplies and occasionally energy security in the Alpine countries.

Along with many Alpine glaciers, climate change will seal the fate of Africa’s last glaciers by 2050. Ocean water levels could continue to rise at an average rate of 2-3.5 mm/year. Polar regions will become wetter, and the cryosphere will continue to melt.

Thanks to developed economies, world hunger is declining and new stress-tolerant crop variants are gaining a foothold in agriculture, especially in Europe and North America. An additional 1 to 1.5 million square kilometers of agricultural land is expected to become ideal for cereal production; however, the area affected by drought is expected to increase by almost the same amount, especially in southern Europe, Africa and southeast Asia. The growing amount of dust entering the atmospheric circulation system could reduce warming by up to 1-5 percent. Due to rising sea levels, marine heat waves and changing acidity, the Mediterranean Sea’s fish fauna could shrink by up to 10-25 percent, while new tropical fish and mollusk species may emerge in the food supply (this is already visible, for example, in the case of blue crabs).

The use of precision farming tools will make it possible to increase cereal and fruit production in Europe, the East Asian region and North America by 4-8 percent compared to 1990 levels. Urban environments are expected to supply 4-5 percent of the world’s city-dwelling population with vertically farmed food by 2050, potentially increasing to 25-30 percent by 2100.

Figure 5: Variation of the minimum (Tmin) and maximum (Tmax) temperatures for crossing the 1.5 and 2 °C thresholds between 2071 and 2100. Source: own work based on IPCC AR6

2) Missing the 2 °C target by a substantial margin is expected to result in far more extreme weather compared to today’s conditions, as well as a deterioration in the economic and social situation.

Under this scenario, carbon dioxide emissions hover around current levels, tropical areas increasingly give way to swamps and boglands, fossil methane emissions rise before starting to decline in the middle of the century; however, they will fail to reach net zero levels by 2100.

China and India delay starting to significantly cut their carbon dioxide, methane and nitrous oxide emissions until after 2050, while several developing countries step up their output of greenhouse gases. U.S. emissions reductions in the 2030s and 2040s fall short of the targets set in the early 2020s. Progress towards sustainability is slow, and development and incomes increase unevenly.

In the second half of the century, Europe will be the only continent to generate electricity from clean sources. Developing countries fail to make efforts at minimizing the soil and water footprint of bioenergy production.

Socio-economic factors follow historical patterns without major shifts. Increasing climatic pressures are causing severe unrest and political destabilization, potentially leading to the inoperability of certain countries in the Middle East and Africa. Energy prices are soaring in emerging regions due to high demand and widespread extremities.

The gap between developed and developing countries widens, with only a handful of North African nations managing to close in on the living standards enjoyed by developed countries.

A positive change could be a steady decline in the demand for heating at medium latitudes (for example, in central Europe), but this will be met with a growing demand for cooling. Developed countries are now sourcing the extra energy for cooling from clean sources (nuclear and renewables) and sustainable cooling technologies are coming to the fore. Up to 10-15 percent of the population in Africa and the Middle East could be displaced by hunger and extreme weather (climate migration).

Glaciers in Europe may recede by up to 50 percent, causing problems with energy and water supplies and resulting in the permanent dehydration of the soil. Catchments of major watercourses in Europe and Asia could receive 30-50 percent less water in summer due to persistent anticyclones. Between 2070 and 2010, the chance of the Arctic Ocean becoming ice-free in summer once every ten years increases by 16 percent (and by as much as 68 percent above 3 °C). The gradual rise of temperatures, together with deforestation and expanding agriculture, will eliminate key ecosystems such as coral reefs, nearly a third of taiga vegetation and tropical rainforests. The destruction of coral reefs and atolls weakens the natural defenses of waterfronts against storms, leaving coastal communities (plants, animals and people) vulnerable to ever more prevalent extremities. In Southeast Asia and equatorial climates, the risk of flooding and storm surges could increase by 35-40 percent. The intensity of marine heat waves in the world’s oceans is multiplied.

Of the 9.5 to 10 million people expected to populate the Earth in 2100, 3 to 3.5 billion will live in regions where growing crops and raising animals will be impossible under today’s conditions. With the boundary of ideal agricultural areas shifting further north (further south in the Southern Hemisphere), agricultural output could increase by 8-10 percent between 2050 and 2100. The area suitable for growing corn could move 340-400 kilometers northward, while in the Carpathian Basin, the Balkans and the Iberian Peninsula, the area under corn and cereal production could decrease by over a third after 2070.

Perhaps most importantly from our point of view, all this will also have a major impact on human health. Causes of death that are today common only in old age will become more frequent among the middle-aged. Lifestyle diseases will become a far stronger risk factor in the future.

Most likely scenarios for the future of European regions

Atlantic region: augmented costal erosion, flooding, increased risk of winter storms, summer heatwaves, habitat changes, expansion of tourism due to rising temperatures, improved conditions for growing cereals.

• Central European region (including Hungary): increasingly severe heat waves and related health risks, further reduction in days of frost during winters, more blocking anticyclones in summer, risk of reduced crop yields, biodiversity loss, gradual disappearance of winter frosts, increasingly prevalent dry spells and flash floods in summer, doubling of winter waterlogging periods.
• Mediterranean region: increasingly common droughts, forest fires, severe desertification, falling hydropower resources, decreasing summer tourism revenues, growing salinity of coastal waters, appearance of new fish and crab species in fisheries, augmented health risks related to heat waves, salinization, increasing intensity of forest fires and more storms during the fall.
• Scandinavia and the subarctic region: increased water saturation of soils, augmented coastal erosion, higher risk of winter storms, stronger storm cyclones, shorter winter sports and ski seasons, improved overwintering of pests, increased hydropower capacity, new agriculturally ideal areas.
• Arctic and tundra areas: increasing prevalence of ticks and mosquitoes, melting permafrost, growing carbon dioxide and methane emissions, intensified polar storms, significantly reduced ice coverage and snow mass.
• Mountainous areas: receding glaciers and snow coverage, loss of subterranean drinking water bases, changing biodiversity, shortened ski seasons, significant loss of winter tourism revenue, growing risk of rock falls and increasingly destructive effects of fluvial erosion.
• Steppe: falling crop yields, rising sea levels (Black Sea), increasing intensity of heat waves, more common droughts, erosion and desertification.

Overall, the later significant reductions in greenhouse gas emissions begin, the greater the likelihood of facing irreversible impacts on the planet in the course of this century. Despite major GHG-emitting countries routinely pledging to reduce their emissions since the launch of United Nations Climate Conferences in 1995, so far there has been no meaningful breakthrough and atmospheric concentrations of gases responsible for warming are gradually growing.

Hopefully, the 28^th UN Climate Change Conference (COP28), to be held in Dubai this year, will deliver the long-awaited breakthrough and humanity will succeed in keeping the temperature rise at least under 2 °C, if we have failed to push it below the desired 1.5 °C. It can be said with certainty that the EU and Hungary will continue on the path toward climate neutrality in the future and will use a variety of adaptation methods to combat the extremes of a changing climate.

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* Greenhouse gases are natural and anthropogenic components of the atmosphere that partially absorb long-wave radiation emitted by the Earth’s surface. Without the greenhouse effect, the average temperature on Earth would be -18 °C instead of 15 °C near the surface, and there would be no life on the planet. The most important greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, tropospheric ozone and sulfur hexafluoride.