3-3.3 million years ago global average temperature was 2-3 °C higher than today. The sea level was 25 meters higher and there was hardly any ice sheet in the northern hemisphere. Just as in predictive models, in the paleaontological data you also see a larger difference with today’s temperatures in the northern hemisphere than in tropical regions and southern hemisphere.
Carbon dioxide concentration during the mid-Pliocene has been estimated at around 400 ppm (yes, the 400 ppm that we have crossed in 2016 for the first time in 3 million years).
The climate was not only warmer, but also wetter, resulting in a northward shift of the taiga (boreal forest) and tundra and a spread of tropical savannahs and woodland in Africa at the expense of deserts (am I reading this correctly: less desert?!)
The Guardian dedicates an article to where you can best live in the U.S. when climate change gets serious. Broadly speaking you can best move to a band roughly above the 42nd parallel.
Places close to a reliable source of water without being flood-prone score high. Seattle, Buffalo, New York (with flood defenses), and Duluth, Minnesota are mentioned as places you might want to be at the end of the 21st century. Places that score low are the south-west and south-east because they will be baked. Southern Florida will be submerged and the Gulf coast will be battered by hurricanes.
Researchers show in Science Advances that the probability of extremely warm and extremely dry conditions has doubled worldwide.
They warn for the threat this poses to worldwide agricultural production. Before anthropogenic climate change chances of extreme weather in multiple agricultural key regions were slim. At the same time the global marketplace could compensate for a bad harvest in one region. The researchers see erosion of this buffer. They specifically point out that the frequency of these simultaneous extreme hot and dry conditions will increase with 20% in the next three decades.
If climate change is unchecked (RCP 8.5) South Asia will experience heat waves that “exceed the survivability threshold” (sic!) from 2070 onwards. Researchers at MIT conclude in a 2017 study that 4% of the South Asia-population, about 70 million people, would face heatwaves of humid heat that will kill even healthy people in the shade within hours. The wet bulb temperature (WTB) would reach 35°C, which means that the human body cannot cool itself and shuts down.
Three quarters (1.3 billion people) in South Asia would experience at least one heatwave before the end of the century with wet bulb temperatures of 31°C, conditions of ‘extreme danger’. To compare: In 2015 there was a severe episode in wich 30°C WTB was measured. This led to 3,500 deaths in South Asia. According to this article the largest hospital in Karachi was receiving 1 patient per minute and the morgue was overflowing.
Wet bulb temperatures currently rarely exceeds 31°C. 35°C WTB has never been measured yet.
Researchers of the Massuchusetts Institute of Technology (MIT) warn that if greenhouse gas emissions will not be curbed, large parts of the Persian Gulf could become uninhabitable at the end of this century. Once every decade heat waves might occur in which the combination of temperature and humidity (the so-called “wet bulb temperature”) will exceed the equivalent of 35 degrees Celsius at 100% humidity. If such conditions are sustained for several hours they become fatal to the human body.
The latest edition of the National Climate Assessment of the United States, a report written by over 300 scientist, warns that because of climate change millions of inhabitants of the United States will migrate inland. The U.S. is not prepared.
States from which people will leave are, according to the authors, amongst others Massachusetts, New Jersey and New York.
The report does not predict when the flows of migrants can be expected. The authors do conclude that communities are not acting sufficiently.
The effects of climate change are many. And the changes it triggers add up. Many studies and news articles deal with a single risk of climate change. The authors of a recent study in Nature Climate Change though, analysed thousands of peer-reviewed papers and detail 467 ways in which climate change has already impacted human health, food supply, quality of freshwater, infrastructure and safety.
The researchers have built an interactive map. It shows what hazards are to be expected in different locations unders different scenarios.
The picture of mass cross-border climate migration is not correct. According to NRC journalist Paul Luttikhuis citing migration researcher Ingrid Boas in a Dutch newspaper NRC Handelsblad in October 2018.
According to Boas, leaving somewhere to never return is an extreme move. When people have to leave their home, they return as soon as possible. And if departure is ultimately inevitable, people will go to nearby regions and will not migrate internationally. She bases her studies on areas in Bangladesh where climate change increasingly influences daily life.
The figure of more than 200 million climate refugees in 2050 (by Norman Myers) is, according to critics, ‘guesswork’. It assumes that people are more willing to leave a country than they actually are.
Right now, in the middle of the winter, we have almost forgotten how extremely dry and hot the summer in Europe was. In July more than 74 people died in a single fire in Greece. Heat waves caused forest fires from Spain to Norway and from Greece to Latvia.
The number of forest fires in Sweden may be exemplary: At the end of July 2018, around 80 forest fires raged in Sweden and a total of 30,000 hectares were burned. That was twice as much as the record year 2014, more than 10 times as much as normal and the most extensive since the 19th century. Summer temperatures in Sweden typically hit the low 20s; in the summer of 2018 there was a heat wave with temperatures of over 30 degrees Celsius.
In contrast to the actual situation last summer, a European research agency (the Joint Research Center) predicts an increase in forest fires in the Mediterranean region, but not in Scandinavia.