Global temperature rise exceeds 1.5°C for the first time. What will we face?

Scientists had predicted that 2025 would be cooler than 2024 , as the cooling La Niña phenomenon emerged in the tropical Pacific last December.

However, the temperature at the beginning of the year has left scientists "stupefied by the heat".

The global average surface temperature in January 2025 was 13.23°C, 1.75°C higher than pre-industrial levels, making it the hottest January in history and breaking the record set in 2024 - but don't forget that in January 2024, the Earth was experiencing the El Niño phenomenon, which has its own warming effect.

The dark red data on the far right of the figure is the global average temperature in January 2025 | Data source: ERA5, C3S/ECMWF Image source: BBC

When talking about the weather in recent years, the word that comes up most often is “record-breaking” - 2023 was the hottest year since data records began, and this record was quickly broken in 2024. What is even more worrying is that 2024 is the first year to break the “1.5°C target” [1]. The global average surface temperature in that year rose by 1.55°C compared to before the Industrial Revolution.

Faced with the 1.5°C target set less than 10 years ago, is humanity really going to throw in the towel? If the 1.5°C limit is really breached, what kind of world will we face?

Global mean surface temperature 1850-2024 | WMO

Did humanity really lose?

The “1.5°C target” comes from the Paris Agreement, and this number is not just something you say casually.

In December 2015, the United Nations Climate Summit was held in Paris, and the 195 member states of the United Nations adopted the Paris Agreement. The agreement set long-term climate goals, the most commonly mentioned of which are: significantly reducing global greenhouse gas emissions, keeping global temperatures below 2°C above pre-industrial levels (1850-1900), and striving to limit the temperature rise to 1.5°C.

It should be noted that 1.5°C is not a magic number, but a recognized ideal target that represents the best consensus among scientists and policymakers on how to minimize risks and protect vulnerable groups. Science does not tell us that if the temperature rises by 1.51°C, it will definitely be the end of the world; similarly, if the temperature remains at 1.49°C, it does not mean that we can eliminate all the impacts of climate change.

The scene when the Paris Agreement was adopted at the 2015 Paris Climate Change Conference | United Nations Framework Convention on Climate Change

However, humans in 2015 were too optimistic.

Since 2015, we have experienced a series of record-breaking high temperatures - the hottest decade in history since data records began in 1940 is the decade from 2015 to 2024. In this decade, record-breaking high temperatures have killed people, extreme changes in precipitation have led to frequent floods and droughts, wildfires have ravaged the ecology and polluted the air, and the intensity and frequency of typhoons, hurricanes and tropical cyclones have gradually increased.

With the emergence of the El Niño phenomenon, the global average annual temperature in 2023 was 1.45°C higher than the pre-industrial level. Moreover, starting from June 2023, the average temperature of each month broke the historical record for that month, and this trend continued until June 2024. On July 22, 2024, the global daily average temperature reached a record high of 17.16°C. In addition, there were 11 months in 2024 with global average surface temperatures above the critical value of 1.5°C [2].

The California wildfires at the beginning of this year were shocking | sciencenews

The good news is that this does not mean the 1.5°C goal has failed . The 1.5°C limit is a long-term temperature target, usually measured over a 20-30 year average rather than a single year.

But what is worrying is that the goal of "limiting the global average temperature rise to 1.5°C" is facing unprecedented severe challenges . In February this year, two research teams published papers separately. They adopted different research ideas, but in the end they both pointed to this result.

A research team from Germany analyzed the trends of temperatures exceeding different thresholds in history and found that starting from 2024, the Earth is likely to have entered a period of 1.5°C warming every 20 years. They called for a period of time when the temperature rises above 1.5°C, but they did not think it was hopeless. By taking strict and prompt actions to reduce emissions and slow the rate of temperature rise, we can still hope to delay or even avoid a long-term temperature rise of 1.5°C.[3]

Another study from Canada used a similar approach to predict future global warming by considering historical data. The simulation results of the study showed that by June 2024, the temperature increase exceeded 1.5 °C for twelve consecutive months, which means that the long-term (20-year average) temperature is likely to have entered or will continue to be above 1.5 °C [4].

From July 2023 to June 2024, the temperature broke the historical record for 13 consecutive months | Data source: ERA 5; Image source: Copernicus Climate Change Service /ECMWF

In other words, without stringent measures to slow global warming , failure of the 1.5°C target will be inevitable.

What will we face if we exceed 1.5°C?

Scientists have predicted that when the long-term temperature exceeds 1.5 °C, the Earth's climate system may undergo irreversible changes and will never return. This change node is also called the "Earth Tipping Point". In the near future, perhaps within the next five years, the global average temperature may not only reach 1.5 °C, but may even exceed it.

What will happen if the global average temperature rises by 1.5°C?

Coral reefs around the world will face a catastrophe, with large areas likely to die completely, which will greatly damage marine biodiversity and the livelihoods of coastal areas that rely on coral reefs. Research reports show that even at current levels of warming, the tipping point for coral reefs is likely to have been triggered[5], meaning that the speed at which coral reefs recover after bleaching is completely outstripping the speed at which they bleach again . By 2030, those colorful coral reefs and the fish and other creatures that depend on them may only exist in aquariums.

In 2024, 77% of the world’s coral reefs were exposed to temperatures high enough to cause bleaching events. | Veronique Mocellin/AIMS

In addition to the tipping point of rapid extinction of coral reefs, 1.5°C is likely to trigger several other tipping points[5]:

1) The Greenland and West Antarctic ice sheets will collapse rapidly . Even if global temperatures drop in the future, the collapse of the ice sheets may not be stopped. The meltwater from the ice sheets will cause the sea level to rise by several meters by the end of this century, and coastal cities and island countries will be seriously threatened.

2) Permafrost in high-latitude areas will melt faster and will no longer be permanent. Permafrost is a huge carbon reservoir, and the thawing process will release carbon dioxide and methane, further exacerbating global warming.

3) The Atlantic Meridional Overturning Circulation (AMOC) system will gradually weaken. This will lead to dramatic changes in the climate in the Northern Hemisphere , colder winters in Europe and North America, and more extreme weather.

Greenland's ice sheet is melting faster | Karolin Eichier / World Meteorological Organization

In addition, if the temperature rises above 1.5°C, the ecosystem will face multiple pressures and risks of transformation. This is not just a change in temperature numbers, but will also trigger a series of chain reactions.

Forests in the northern part of the Earth may experience problems such as tree species replacement, frequent forest fires, and increased insect pests; mangroves and other wetland ecosystems in coastal areas will be severely affected by rising sea levels, saltwater intrusion, and extreme climate events (such as strong storms and rainstorms), reducing the function of these ecosystems as carbon sinks and natural protective barriers. As for the Amazon rainforest, long-term warming will increase the frequency and intensity of droughts in the region, making it difficult for the rainforest ecosystem to maintain a humid environment, causing some areas to transform into tropical savannas.

In 2024, the Amazon rainforest suffered the worst drought since 1950. This transformation will not only cause a large number of organisms to lose their habitats, leading to a significant decline in biodiversity, but will also destroy the water cycle system in the region. As the "lungs of the earth", the Amazon has reduced its absorption of carbon dioxide after its forests were replaced by savannahs, which in turn caused more greenhouse gases to remain in the atmosphere, exacerbating global warming and forming a vicious cycle.

Comparison of satellite images of the Negro River in the Brazilian Amazon in September 2021 and September 2024 | Data source: Copernicus, Sentinel-2 satellite, Image source: CNN

What will happen to China after 1.5°C?

Studies have shown that the future trend of change in the mid-latitude regions of the Northern Hemisphere (such as Europe, North America, and East Asia) is that the summer will be longer, the other three seasons will be shorter, there will be more warm winters, and extreme weather will increase[6]; in particular, extreme high temperatures in the summer will become more frequent and more severe .

The latest Lancet Countdown Report on Human Health and Climate Change shows that the number of deaths related to heat waves in 2022 will reach 50,000 nationwide , mainly in Henan, Shandong, Jiangsu and Sichuan. Among them, the number of deaths related to extreme high temperature weather in Henan Province accounts for as high as 15.8% of the total number of deaths in the whole year.

At the same time, the distribution of precipitation will also change. In China, the rainfall belt tends to expand toward the north , and the frequency of continuous and extremely heavy precipitation will increase.

Heavy rain in Henan in July 2021 | Shi Yan/People's Daily Online

Some scholars have simulated the climate of different cities sixty years from now and made analogies with different countries around the world, so that everyone can have a more intuitive understanding of the future climate[7].

If there is no major change in the current energy structure and lifestyle of mankind, then in about 60 years, the climate of northern cities will become more like that of the south . Beijing will become the current Xinxiang in Henan, and Xinxiang will become Zhuji in Zhejiang. Zhuji's climate will be like that of the northwestern cities of Pakistan (with the highest temperature reaching 50°C). According to predictions, Shanghai in the future will also have the climate of the current northwestern cities of Pakistan, and the climate of Chongqing and Chengdu will become similar to that of Baise in Guangxi today, while the climate of most cities in Guangdong in the next 60 years will not be similar to that of existing cities in the world.

Peshawar, an important city in northwestern Pakistan｜gsiltd.hk

Coastal cities are also facing severe challenges. Coastal cities are often economically developed and densely populated. There are many high-rise buildings in the city, and the urban population has a large demand for groundwater. The combination of these two factors has caused urban land to sink, especially in some coastal cities on deltas and alluvial plains (such as the Yangtze River Delta and the Pearl River Delta), where human activities have the greatest impact on land subsidence. Coupled with the rise in sea levels caused by global warming, more and more coastal cities will be below sea level.

A recent study shows that in the worst-case scenario (if current carbon emissions continue), by 2120, 22%-26% of China’s coastal land will be below sea level , and 9%-11% of the coastal population will be affected[8]. At the same time, coastal cities are also popular destinations for extreme weather (typhoons, hurricanes, tropical cyclones). This makes people wonder whether coastal cities will really be livable in the future.

A sea-blocking dam in the Netherlands. More than half of the land in the Netherlands is less than one meter above sea level, and a quarter of the land is below sea level. Fortunately, various dams and water conservancy systems have greatly reduced the risk of flooding faced by people. | World Wind (NASA)

The fact that the land of coastal cities is below sea level does not mean that the cities will disappear, because humans can build coastal dams - the Netherlands is a good example. However, the gradually rising sea level and extreme weather conditions will bring challenges to the maintenance and performance improvement of coastal urban infrastructure; and for those underdeveloped island countries and coastal areas, backward infrastructure will make local people more vulnerable to climate change - they contribute the least to global warming, but face the greatest threat.

Although many people still believe that climate change is just part of the natural evolution of the earth, scientific research has clearly shown that human activities (such as fossil fuel combustion, industrial waste gas emissions and large-scale deforestation) are significantly accelerating global warming and changing the environment we live in. At the same time, the frequent occurrence of extreme weather events and the continuous rise in sea levels are constantly reminding us that the climate crisis is gradually approaching.

Worse still, the United States, a major emitter, plans to withdraw from the Paris Agreement, bringing more uncertainty to global emission reduction targets. As ordinary people, in addition to objectively and rationally understanding the facts and improving our ability to cope with extreme weather, each of us can also affect the decision-making of governments and enterprises by paying attention to climate change and choosing low-carbon products and environmentally friendly behaviors.

Will the global average temperature continue to exceed 1.5°C? We still have a chance before the coming of each next year.

References

[1] https://wmo.int/news/media-centre/wmo-confirms-2024-warmest-year-record-about-155degc-above-pre-industrial-level

[2] https://climate.copernicus.eu/global-climate-highlights-2024

[3] Bevacqua, E., Schleussner, CF. & Zscheischler, J. A year above 1.5 °C signals that Earth is most probably within the 20-year period that will reach the Paris Agreement limit. Nat. Clim. Chang. 15, 262–265 (2025). https://doi.org/10.1038/s41558-025-02246-9

[4] Cannon, AJ Twelve months at 1.5 °C signals earlier than expected breach of Paris Agreement threshold. Nat. Clim. Chang. 15, 266–269 (2025). https://doi.org/10.1038/s41558-025-02247-8

[5] Spaiser, V.; over 200, A. Global Tipping Points Report; Lenton, TM, Arnstrong McKay, DI, Loriani, S., Abrams, JF, Donges, JF, Milkoreit, M., Powell, T., Smith, SR, Zimm, C., Buxton, JE, Bailey, E., Laybourn, L., Ghadiali, A., Dyke, JG, Eds.; University of Exeter: Exeter, UK, 2023.

[6] Wang, J., Guan, Y., Wu, L., Guan, X., Cai, W., Huang, J., et al. (2021). Changing lengths of the four seasons by global warming. Geophysical Research Letters, 48, e2020GL091753. https://doi.org/10.1029/2020GL091753

[7] https://fitzlab.shinyapps.io/cityapp/

[8] Zurui Ao et al. A national-scale assessment of land subsidence in China's major cities.Science384,301-306(2024).DOI:10.1126/science.adl4366

Author: Judy

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