Urban trees not only important fornature and climate protection, but also help reduce social inequalities

Discussions about greenhouse gases usually include mention of common terms such as methane and CO₂. However, air pollutants such as particulate matter and ammonia do no less damage to the climate, since they can also act as greenhouse gases or serve as precursor compounds of them.

Air pollutants are substances in the air that can compromise human health and the environment. They can come from natural or anthropogenic (i.e., man-made) sources. Natural pollutants include soot and sulfur dioxide, which are produced by volcanic eruptions. Particulate matter and carbon monoxide caused by traffic are examples of anthropogenic air pollutants.

Climate change is causing weather patterns to change and high-pressure areas to occur more frequently. The latter, in turn, provide the ideal conditions for long-lasting heat waves and heat islands, resulting in persistent heat load in cities in particular, which cool down only slowly. Heat islands are occurring more often in smaller cities as well. In large cities, the temperature difference can amount to as much as 10 degrees Celsius.

Emissions are one of the driving forces behind global warming. They are particles, substances, or radiation released into the atmosphere. Emissions can occur naturally, such as soot from volcanic eruptions or CO₂ from forest fires. There are also anthropogenic emissions that are caused by human activity. These include particulate matter, CO₂ and fluorinated gases from traffic as well as from heat and power generation, and also methane from livestock farming.

The carbon budget shows the maximum amount of CO₂ we humans can emit as of today to achieve the climate targets of the Paris Agreement and limit the rise in global average temperature to well below 2 degrees Celsius. The figure is based on the linear correlation between temperature and CO2 emissions. This means that the global average temperature keeps rising as long as we emit CO₂ into the atmosphere. CO₂ prevents heat from being radiated into space and remains in our atmosphere for periods ranging from hundreds to thousands of years once it has been emitted. If we wanted to maintain today’s temperatures, the concentration of CO₂ in the atmosphere would have to drop from 410 to 353 parts per million. This means we have to reduce our CO₂ emissions to zero, or Net-Zero, if we want to stop temperatures from rising.

The terms “climate” and “weather” are based on different time periods:

Many scientists expect to see a decline in biodiversity due to climate change, although the extent to which species will be able to adapt to the change is subject to dispute.

Climate change can impact human health directly and indirectly:

If temperatures continue to rise, we could hit critical thresholds that significantly accelerate climate change. In climate research, these critical thresholds are called tipping points or tipping elements. They are a part of the global climate system. Passing even just a few tipping points will have extensive environmental impacts that jeopardize the basis of life for many people, animals, and plants. Such an event could also trigger a chain reaction, where the passing of one tipping point leads to further tipping points being passed. Scientists refer to this as a feedback process.