Extreme temperature

July and August of 2023 registered the highest average global temperature since records began.3 Over the past decades, population exposure to extreme temperatures has increased significantly. National-level analysis shows an increase in energy consumption for cooling, as well as, crucially, a tendency for extreme heat clusters to last longer than they have over the past two decades (Scoccimarro et al., 2023[32]). During the summer of 2023, several regions in the northern hemisphere experienced record daily temperatures, for example in Phoenix (USA, 48.3°C), Death Valley (USA, 54.4°C), Rome (Italy, 42.9°C) and Sanbao (China, 52.2°C). This is not an isolated event: OECD data confirms that this is a consequence of an observed trend. Since 1979 the population in both OECD and OECD partner countries has been increasingly exposed to hot days,4 with an estimated 11.3% more people exposed to hot days in the period 2018-22 compared to the reference period 1981‑2010 (Figure 20).

Countries whose population was most exposed to hot days in 2018-22 include Saudi Arabia (98.3%), India (97.3%) and Israel (91%), an estimated 1.4 billion people in total (Figure 21). Although exposure to extreme temperatures in countries such as Saudi Arabia and Israel was already historically high, the duration of exposure is increasing.

Southern Europe is increasingly affected by extreme heat. In 2023 the region experienced an unprecedented heatwave that generated enormous impacts and has yet to be fully assessed. Indicators show that, between 2018 and 2022, approximately 74.7%, 55% and 68.7% of the population in countries such as Greece, Italy and Spain respectively were exposed to hot days. Furthermore, certain regions within these countries are also experiencing an increase in additional hot days per year compared to the reference period 1981-2010 (Figure 22), highlighting regional differences with regards to extreme heat. This indicates that hot European summers are likely to get worse, highlighting again the urgency of taking appropriate measures to tackle extreme heat, particularly for countries that are traditionally less prepared for extreme heat.

 

Figure 22. Increasing extreme temperatures across southern Europe

Annual number of additional hot days (2018-22 average) compared to the reference period 1981-2010 across the European region

Note: A variety of indicators have been developed that assess extreme temperatures; these should be consulted for more detailed analysis of individual countries.

Source: (Maes et al., 2022[20]).

Tropical nights, associated with high night-time temperatures, are also a relevant indicator of increasing temperature, and generate risks to human health due to sleep disturbances and inability to cool down at night (Seltenrich, 2023[33]). Twenty countries — out of 51 countries covered — had more than an additional 10% of their population exposed to tropical nights5 over the period 2018-22 compared to 1981‑2010, while countries such as Korea (28%), Italy (18%) and Greece (16%) had the highest increase in population exposed to more than eight weeks of tropical nights.6

Consistent with evidence of increasing average temperature, exposure to extreme cold is decreasing. The share of population exposed to icing days is decreasing year by year, with an estimated 5.8% fewer people exposed to icing days in the period 2018-22 compared to the reference period of 1981-2010 (Figure 23).

 Droughts and wildfires

Rising temperatures also have adverse effects on food systems, with croplands increasingly susceptible to agricultural droughts. Across the OECD and OECD partner countries there is a significant decrease in soil moisture on croplands (2.4%) over the period 2018-22 compared to the reference period 1981-2010. Some of the countries most affected by agricultural droughts include Argentina, Brazil and Romania, which all experienced average declines of more than 6% in cropland soil moisture in the past five years (Figure 24).

National averages hide large differences and changes at the subnational level, where recorded drops in soil moisture are greater (Figure 25). In South America, for example, the Argentinian provinces of Córdoba, Chaco and Tucumán, which have high cropland cover, have experienced severe soil moisture declines of 19%, 18% and 17% respectively. Similarly, the Chilean regions of Valparaíso, Santiago Metropolitan Area and O’Higgins are experiencing soil moisture declines of 8%, 7% and 5% respectively. These dramatic changes have already significantly impacted local communities and agricultural production. For example, Argentina, one of the world’s top grain exporters, is in the grip of its worst drought in over 60 years, facing losses of USD 14 billion and more than 50 million tonnes less grain output across soy, corn and wheat (Sigal and Raszewski, 2023[34]). Drought can also exacerbate other climate-related hazards such as conditions that increase the possibility of wildfires due to dry vegetation and fuel load and changing weather patterns.

 

Figure 25. Intensifying drought impacts across Central and South America

Land soil moisture anomaly (%), 2018-22 average compared to the reference period 1981-2010 across the Caribbean, Central and South America

Note: Negative values indicate increasing drought conditions in the top soil layer, while positive values indicate wetter conditions in the top soil layer compared to the reference period 1981-2010.

Source: (Maes et al., 2022[20]).

Wildfires raged across the world in 2023. In the southern hemisphere, wildfires in Chile generated a national emergency. In the northern hemisphere, more than 150 000 km2 of land in Canada burned by the end of August, with New York City shrouded in a cloud of smoke and recording some of the highest air pollution levels in the world in July. Meanwhile, wildfires in southern Europe led to civilian casualties and threatened tourism destinations, highlighting that the impact of extreme wildfires goes beyond lives lost and includes widespread health impacts and innumerable economic disruptions (OECD, 2023[35]). This is consistent with the increasing wildfire exposure registered by OECD data.

Burning of land is due to a variety of causes including wildfires or controlled and uncontrolled biomass burning. Globally, between 2018 and 2022, 20% of burned land was located in just seven OECD and partner countries. Whether this is due to wildfires or intentional biomass burning, burning can impact global mitigation efforts to combat climate change. On average, more than 1% of land area was burned per year between 2018 and 2022 in Argentina, Australia, Brazil, Colombia, India and South Africa, representing approximately 620 000 km2, which is roughly equivalent to the size of France.

Wildfires are becoming more widespread, increasing ecosystem damage, notably biodiversity and carbon sinks, as well as harming human life. Between 2018 and 2022, an estimated 3.2% of the population across OECD and OECD partner countries lived in areas with very high or extreme wildfire danger, representing more than 160 million people. Countries with the highest population exposure to very high and extreme wildfire danger are South Africa (41.2%), Australia (19%), Costa Rica (12.4%), Brazil (9%) and Chile (8.7%), exposing a combined population of more than 51 million people. In absolute terms, India's population experiences the highest overall exposure to wildfires: between 2018 and 2022 more than 38 million people lived in areas with very high and extreme wildfire danger.

Across the OECD and partner countries there is an overall increase in forest exposure to very high or extreme wildfire danger (Figure 26). For example, Brazil experienced the largest area of forest exposed (~1.9 million km2) to wildfire danger over the past five years. Other countries, such as the United States, Australia and Mexico, also have considerable amounts of forest exposed, with 516 000 km2, 622 000 km2 and 614 000 km2 of forest areas exposed to very high or extreme fire risk respectively. Across OECD countries, Israel, Mexico and Portugal have some of the highest percentages, with more than 74% of forest exposed to wildfire danger between 2018 and 2022 (OECD, 2023[36]). These large areas of forest exposure highlight the considerable risk forests face and should be considered a policy priority given both human risk and key role that forests play as carbon sinks around the world.

 Extreme precipitation, flooding and storms

Extreme precipitation events pose serious dangers to countries by potentially causing flash floods, landslides, and impacting the population and economic infrastructure. A majority of OECD and partner countries experience some level of exposure to extreme precipitation events, but the duration of exposure varies considerably. OECD and partner countries with the highest share of land exposed to extreme precipitation events between 2018 and 2022 included Indonesia (36%), Colombia (28.5%), Peru (21.2%) and Brazil (15.6%).7 These countries experience higher precipitation due to being located in a tropical region with warmer temperatures and abundant moisture, amongst other factors.

In Europe, land exposure to extreme precipitation events remains low (< 3%). However, changing rain patterns affect ecosystems. For example, in central Europe, the wetter-than-average spring of 2023 offered partial relief after a dry winter, but the impact of severe drought in 2022 on groundwater levels means that rainfall was insufficient to replenish aquifers. At the same time, spring is less efficient than winter in replenishing aquifers, as rainwater is consumed by growing vegetation and higher evaporation rates due to higher temperatures (Copernicus Climate Change Service, 2023[37]).

Although dependent on crop types, extreme precipitation events can pose dangers to agriculture by causing flooding, soil erosion, water saturated soils and crop damage, threatening food production and livelihoods. This can be especially problematic for countries dependent on agriculture, making them overly vulnerable to precipitation changes due to climate change.

On average, Indonesia (31.6%), Colombia (13.2%), Costa Rica (9.8%), Peru (8%) and Brazil (3.3%) had the highest share of cropland exposed to extreme precipitation events between 2018 and 2022. The share of cropland exposed to extreme precipitation events has increased for countries such as Indonesia, with an estimated increase from 3.8% in 2000 to 41.1% in 2022. Six out of ten countries whose cropland area is most exposed to extreme precipitation events are also more dependent on agriculture as a share of GDP. For example, Indonesia and Colombia have, on average, an estimated 31% and 13% of cropland exposed to extreme precipitation events while their GDP share of the agriculture, forestry and fishing sector is 12.9% and 7.2%, which is significantly higher than the average in OECD and OECD partner countries (3.2%).

Meanwhile, extreme precipitation events are also increasing significantly in certain subnational regions, such as in South America and Southeast Asia (Figure 27). In Southeast Asia, for example, the Indonesian provinces of Kalimantan and Sulawesi are experiencing an increase in extreme precipitation events (Figure 27) while an estimated 35% and 33% of the land is used for croplands. This highlights that certain subnational regions already impacted by extreme precipitation may see further increases due to climate change, increasing risks to food security, and possibly dramatic changes in migration flows.

 

Figure 27. Increasing extreme precipitation events across Southeast Asia

Yearly number of additional days with extreme precipitation events (2018-22 average) compared to the reference period 1981-2010 across Southeast Asia

Note: Negative values have been removed because the focus is on the occurrence of extreme precipitation events. A variety of indicators have been developed that assess extreme precipitation; these should be consulted for more detailed analysis of individual countries.

Source: (Maes et al., 2022[20]).

The South Asian monsoon season is becoming increasingly unpredictable and less dependable (Fountain, Levitt and White, 2022[38]). The 2023 monsoon season brought more extreme weather events, bringing the heaviest rainfall in decades to northern India, causing rivers to overflow, with flooding and landslides washing away vehicles, destroying bridges and roads, and disrupting power and electricity (The Guardian, 2023[39]). Over 100 people across Himachal Pradesh, Uttar Pradesh, and Delhi died over a two-week period of intense rain and flooding, with thousands of others evacuated to relief camps (Mehrotra, 2023[40]).

Flooding is caused by a combination of factors including extreme precipitation, storm surges, river overflow and increased artificial surfaces. It threatens people’s lives, livelihoods and economic infrastructure. Among the 51 OECD and OECD partner countries, the Netherlands and Hungary have the highest percentage (~20%) of total land area exposed to extreme river flooding. Meanwhile, China is the most exposed country with 22% of its built-up area exposed to river flooding, followed by Latvia (20%) and the Netherlands (18%). In terms of agricultural land exposure, the most affected OECD and OECD partner countries are Hungary, the Netherlands, and the Slovak Republic with more than 17% of their cropland exposed to possible extreme events.8

River flooding can also cause human losses. In 2021, Germany was hit by floods that generated the highest costs caused by a climate extreme event in the post-war period, killing 189 people and causing direct economic damages estimated at 33.1 billion EUR (OECD, 2023[24]). Among OECD and OECD partner countries, populations in Latvia, the Slovak Republic and the Netherlands are the most exposed, with more than 30% of people potentially affected. Due to the sheer size of China (26%) and India (20%), the total number of people exposed in these two countries to river flooding is approx. 670 million (Figure 28).

Low-lying coastal communities face a range of coastal flooding hazards such as storm surges and erosion. These hazards are expected to worsen as climate change increases the frequency and severity of coastal floods. The most exposed countries are the Netherlands, Belgium and Denmark. The Netherlands has 51% of its land area potentially exposed to coastal flooding with a ten-year return period, followed by 6.4% for Belgium and 5.6% for Denmark. However, these figures should be interpreted with caution, as they do not account for existing flood protection measures or sea-level rise. Nevertheless, they underscore the importance of maintaining existing protections to prevent future impacts and the potential economic costs of dealing with climate change.

Built-up area exposure to coastal flooding is increasing. Across OECD and OECD partner countries, the percentage has increased significantly, from 1.8% in 2000 to 2.6% in 2020 (Figure 29). This suggests that additional investment in infrastructure will be necessary, particularly if built‑up area continues to expand in coastal zones. Across OECD and OECD partner countries, the Netherlands has 52% of its built‑up area exposed to coastal flooding, followed by Belgium (10%) and China (6.6%). This is explained by the fact that much of the land along the North Sea coast is either below sea level or just slightly above it, exposing a sizeable amount of the land and its built‑up areas to coastal flooding hazards.

Storms affect all OECD and partner countries with varying degrees of intensity and occurrence, and at times worsen the effects of other hazards. For example, in the United States in 2022, Hurricane Ian caused extensive storm-surge inundation in low-lying coastal areas and river flooding, becoming the fourth strongest landfall on record in Florida. Countries most exposed to violent storms are located principally in northwest Europe and east Asia. Countries such as Belgium, Iceland, Ireland, the Netherlands, and the United Kingdom had more than 45% of their population and built-up areas exposed to violent storms in the period 2018-22 (Figure 30). Meanwhile, exposure to tropical cyclones is limited to a subset of OECD and OECD partner countries due to their geographic position. The most exposed OECD and OECD partner countries are Japan and Korea (90%), where more than 90% of their populations and built-up areas are exposed to tropical cyclones (with wind speeds higher than 119 km/h or 33 m/s), followed by Mexico and China with 25%.