Certain types of extreme weather events have increased significantly worldwide. The warming that scientists have observed to date has already led to longer and more frequent heat waves of greater intensity in most areas on land. In some areas, droughts have also become more frequent and severe, such as in the Mediterranean region, West Asia, many parts of South America, and much of Africa and Northeast Asia. In addition, local heavy precipitation has intensified further all across the globe.

When the sun’s energy reaches Earth, some trace gases in the Earth’s atmosphere ensure that part of the energy from solar radiation is not completely reflected back into space in the form of infrared radiation. Instead, some of it remains in the atmosphere as thermal energy. These gases are called greenhouse gases, and their impact is known as the greenhouse effect. The most important greenhouse gases are water vapor, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

Compared to the 1970s, apple trees are now blooming around 13 days earlier, for example. However, the blossoms are very sensitive to frost, and since the weather often turns very cold at night so early in the year, fruit growers increasingly have to contend with severe frost damage to their crops (as was the case in spring 2017). The drought seen in recent years has led to considerable regional crop losses. In 2018, for example, grain yields were 18 percent below average, with Schleswig-Holstein (-31 percent), Brandenburg (-27 percent), and Saxony-Anhalt (-26 percent) being hit hardest.

Across the globe, rising temperatures have already led to a shift in climate zones and, as a result, to some profound changes in the distribution ranges of plants and animals. In Germany, too, we are already seeing the further spread of various plants. The monkey orchid, for example, originally from the Mediterranean region, is extending its reach northwards, and the holly, which has been native to western Germany for some time, is spreading to the north and to the east. The same thing is happening with disease-carrying insects as well, such as the Asian tiger mosquito. Climate change is also altering the developmental phases of organisms and the relationships between them. Migratory birds are returning earlier, and researchers have documented an earlier spawning season for fish. Plants’ flowering times are shifting and no longer in sync with the life cycle of the insects that pollinate them.

As temperatures rise, some elements in the Earth’s climate system will undergo rapid and dramatic rather than gradual change. Scientists have identified more than a dozen such “tipping elements.” At certain temperature thresholds (which experts cannot precisely quantify yet), they will “tip” past a point of no return, making a return to their previous state practically impossible.

Warmer summers and longer dry spells are increasing the risk of forest fires, and the number of days with high fire danger levels has already gone up in recent decades. Across Germany, there were some 27 days per year on average with a high or very high risk of forest fire in the period from 1961 to 1990. From 1981 to 2010, there were about 33 such days per year, increasing yet again to some 38 days for the period from 1991 to 2019.¹

In Germany, one of the consequences of climate change is the increase in heavy rains. Having said that, the number of consecutive days with no precipitation is also going up, especially in summer. Both are leading to an increase in hydroclimatic extremes that pose a threat, such as droughts and floods. Scientists predict that this trend will continue into the future.¹ According to data from Germany’s National Meteorological Service, the number of days with low soil moisture has already increased significantly since 1961. Germany’s northeast and the Rhine-Main region are being hit particularly hard by the increasing dryness of the soil.²

In the 1950s, Germany experienced, on an annual average, around three “hot days,” which is what meteorologists call those days when the temperature rises to 30 degrees Celsius or higher. Between 1991 and 2019, the number of “hot days” had already increased to 8.8 days per year on average. In contrast, the average number of “below-freezing days,” i.e., days when the temperature remains below 0 degrees Celsius all day, decreased from 28 to 19 days per year during the same period.¹ In winter 2019/2020, Hamburg, for example, did not experience a single below-freezing day – a first since record-keeping began.²

Since 1900, sea levels have already risen worldwide by some 16 centimeters on average, increasing by about 9 centimeters alone since global satellite measurements began in 1993. Since 2006, the rate of sea-level rise has come to around 3.6 millimeters annually (i.e., approximately 3.6 centimeters per decade), more than twice as much as before. Behind this acceleration is the melting of the ice sheets in Greenland and Antarctica, which is proceeding at ever faster rates.¹