Ein spannender Artikel bei The Conversation beschäftigt sich mit der kleinen Eiszeit und welche Auswirkungen sie auf Europa hatte. Als im heutigen Vereinigten Königreich ab dem 14. Jahrhundert die Durchschnittstemperaturen um 2 Grad sanken ging das einher mit Missernten, Hunger und Not. Es gab Aufstände, Revolutionen und Kriege und sogar Sündenböcke. In diesem Fall Hexen, denen man vorwarf das Wetter verursacht zu haben.
“Behind this whimsical scene lay upheaval: an early modern cost of living crisis. Watermen like Taylor, who ran a river taxi service across the Thames, saw their livelihoods collapse. Many of the stallholders at frost fairs were out-of-work watermen. The price of fuel (predominantly firewood) increased as demand for heating soared. And in Taylor’s “gnashing age of snow and ice”, the shivering poor begged the rich for charity.
Life for London’s poor and newly unemployed was increasingly desperate, with many lacking money to eat and keep warm. The scene was similar across Europe. As Philip IV of Spain toured Catalonia’s barren fields, an associate observed that “hunger is the greatest enemy”.
Contemporaries worried about the social ramifications. The “cryes and teares of the poore, who professe they are almost ready to famish”, wrote John Wildman in 1648, prompted fears that “a sudden confusion would follow”. In 1684, King Charles II of England authorised the bishop of London to collect money for the poor in the city and its suburbs and also donated a sum from the royal treasury.
Local parish relief (a compulsory tax on the wealthier inhabitants of each parish to provide for their poorer neighbours) reduced starvation and saw England suffer fewer deaths than France. Still, the terrible winter of 1684 claimed many lives. Burials were suspended as the ground was too hard to dig. Trees split apart and some preach.”
Auch über die Ursachen der kleinen Eiszeit macht sich der Artikel Gedanken. Es gibt verschiedene Theorien wie Vulkanausbrüche oder die Sonne, die zwischen 1650 und 1715 kaum Sonnenflecken hatte. Ein lesenswertes Stück.
Der englische Schauspieler Rowan Atkinson (Mr. Bean) hat seine Ansichten zum Thema Elektroauto im Guardian geäußert. Er ist eigentlich ein Liebhaber von E-Autos, kommt aber zu einem ernüchternden Fazit.
“Increasingly, I’m feeling that our honeymoon with electric cars is coming to an end, and that’s no bad thing: we’re realising that a wider range of options need to be explored if we’re going to properly address the very serious environmental problems that our use of the motor car has created. We should keep developing hydrogen, as well as synthetic fuels to save the scrapping of older cars which still have so much to give, while simultaneously promoting a quite different business model for the car industry, in which we keep our new vehicles for longer, acknowledging their amazing but overlooked longevity. Friends with an environmental conscience often ask me, as a car person, whether they should buy an electric car. I tend to say that if their car is an old diesel and they do a lot of city centre motoring, they should consider a change. But otherwise, hold fire for now. Electric propulsion will be of real, global environmental benefit one day, but that day has yet to dawn.”
Eine Empfehlung zum Folgen auf Twitter ist Uwe Gärtner. Man kann die Ausdauer des Wissenschaftlers nur bewundern, wenn er jeden Tag auf ein Neues die Unterschiede zwischen Leistungszahlen und Wirkungsgraden erklärt. Auf Twitter werden nämlich jeden Tag neue Erfindungen gemacht. Das tägliche Perpetuum mobile, wenn man so will, weil grundlegende Dinge verwechselt werden. Die Ausbildung an der Google Uni hat offenbar noch Schwachstellen.
Broadman & Kaufman auf The Conversation:
Was Earth already heating up, or did global warming reverse a long-term cooling trend?
Over the past century, the Earth’s average temperature has swiftly increased by about 1 degree Celsius (1.8 degrees Fahrenheit). The evidence is hard to dispute. It comes from thermometers and other sensors around the world.
But what about the thousands of years before the Industrial Revolution, before thermometers, and before humans warmed the climate by releasing heat-trapping carbon dioxide from fossil fuels?
Back then, was Earth’s temperature warming or cooling?
Even though scientists know more about the most recent 6,000 years than any other multimillennial interval, studies on this long-term global temperature trend have come to contrasting conclusions.
To try to resolve the difference, we conducted a comprehensive, global-scale assessment of the existing evidence, including both natural archives, like tree rings and seafloor sediments, and climate models. Our results, published Feb. 15, 2023, suggest ways to improve climate forecasting to avoid missing some important slow-moving, naturally occurring climate feedbacks.
Global warming in context
Scientists like us who study past climate, or paleoclimate, look for temperature data from far back in time, long before thermometers and satellites.
There are several natural archives that record changes in the climate over time. The growth rings that form each year in trees, stalagmites and corals can be used to reconstruct past temperature. Similar data can be found in glacier ice and in tiny shells found in the sediment that builds up over time at the bottom of the ocean or lakes. These serve as substitutes, or proxies, for thermometer-based measurements.
For example, changes in the width of tree rings can record temperature fluctuations. If temperature during the growing season is too cold, the tree ring forming that year is thinner that one from a year with warmer temperatures.
Another temperature proxy is found in seafloor sediment, in the remains of tiny ocean-dwelling creatures called foraminifera. When a foraminifer is alive, the chemical composition of its shell changes depending on the temperature of the ocean. When it dies, the shell sinks and gets buried by other debris over time, forming layers of sediment at the ocean floor. Paleoclimatologists can then extract sediment cores and chemically analyze the shells in those layers to determine their composition and age, sometimes going back millennia.
Climate models, our other tool for exploring past environments, are mathematical representations of the Earth’s climate system. They model relationships among the atmosphere, biosphere and hydrosphere to create our best replica of reality.
Climate models are used to study current conditions, forecast changes in the future and reconstruct the past. For example, scientists can input the past concentrations of greenhouse gases, which we know from information stored in tiny bubbles in ancient ice, and the model can use that information to simulate past temperature. Modern climate data and details from natural archives are used to test their accuracy.
Proxy data and climate models have different strengths.
Proxies are tangible and measurable, and they often have a well-understood response to temperature. However, they are not evenly distributed around the world or through time. This makes it difficult to reconstruct global, continuous temperatures.
In contrast, climate models are continuous in space and time, but while they are often very skillful, they will never capture every detail of the climate system.
A paleo-temperature conundrum
In our new review paper, we assessed climate theory, proxy data and model simulations, focusing on indicators of global temperature. We carefully considered naturally occurring processes that affect the climate, including long-term variations in Earth’s orbit around the Sun, greenhouse gas concentrations, volcanic eruptions and the strength of the Sun’s heat energy.
We also examined important climate feedbacks, such as vegetation and sea ice changes, that can influence global temperature. For example, there is strong evidence that less Arctic sea ice and more vegetation cover existed during a period around 6,000 years ago than in the 19th century. That would have darkened the Earth’s surface, causing it to absorb more heat.
Our two types of evidence offer different answers regarding the Earth’s temperature trend over the 6,000 years before modern global warming. Natural archives generally show that Earth’s average temperature roughly 6,000 years ago was warmer by about 0.7 C (1.3 F) compared with the 19th century median, and then cooled gradually until the Industrial Revolution. We found that most evidence points to this result.
Meanwhile, climate models generally show a slight warming trend, corresponding to a gradual increase in carbon dioxide as agriculture-based societies developed during the millennia after ice sheets retreated in the Northern Hemisphere.
How to improve climate forecasts
Our assessment highlights some ways to improve climate forecasts. For example, we found that models would be more powerful if they more fully represented certain climate feedbacks. One climate model experiment that included increased vegetation cover in some regions 6,000 years ago was able to simulate the global temperature peak we see in proxy records, unlike most other model simulations, which don’t include this expanded vegetation. Understanding and better incorporating these and other feedbacks will be important as scientists continue to improve our ability to predict future changes.
A new interactive research tool for the Antarctic sea-ice zone
A new interactive Antarctic map promises to assist voyage planning and enhance climate research in the sea-ice zone, by bringing together Southern Ocean data from the past four decades.
Developed by Australian Antarctic Division sea-ice scientists Dr. Petra Heil, Sean Chua and Anton Steketee, “Nilas” presents near-real-time and historical data on sea ice, chlorophyll (a proxy for phytoplankton production), and sea-surface temperature around Antarctica.
Dr. Heil said the historical ice and ocean data and the ability to superimpose past or proposed ship trajectories or animal or instrument tracks over the data, made it a powerful planning, analysis and research tool.
The tool includes sea-ice data dating back to 1980, chlorophyll data from 1998 and sea surface temperature from 1981.
“We have used this tool to plan a marine-science voyage, and are currently using it to pinpoint deployment locations for autonomous instruments to study ice-edge processes, such as wave-induced ice breakup,” Dr. Heil said.
“The tool allows us to look back at the sea-ice concentration and extent over the past few years to gain an understanding of the likely sea-ice conditions in the month of our voyage. We can then identify the most suitable location to take samples and deploy instruments.
“The tool also allows us to look at ice conditions in locations where we may have limited or no experience in navigating the ice area, and make decisions about the best time of year to visit to achieve our objective.”
Mr. Chua said the ability to look at different ice and ocean variables at the same time could spark new research ideas, or enable scientists to explore links between different Earth system components.
“If you’re an atmospheric scientist sampling air from a vessel and you see a signal that does not make sense, you could look back at the ice or chlorophyll conditions at the time and location of your signal and check for any correlation,” he said.
“Phytoplankton may have released sulfate aerosols into the air, affecting the atmospheric properties, for example. So having all these data in the one interface enables connections between scientific disciplines.”
To build the mapping platform the team used existing data sets generated from satellite observations. Data sets came from a range of sources, including the National Snow and Ice Data Center, Unversität Bremen, the Met Office and the Ocean Color Climate Change Initiative.
Data sets include daily and monthly sea-ice concentration (amount of sea-ice cover), sea-ice freeboard (height above the ocean surface), chlorophyll concentration and sea-surface temperature. They also include in-house derived parameters.
“In consultation with Antarctic scientists, we chose source data and products that would be the most useful for looking at the long-term climate record,” Mr. Steketee said.
“We standardized that data, added some functionality, and presented it on a platform that doesn’t need any technical expertise to use.
“This tool does not require any software or downloads to run, it can be configured to run without an internet connection, and it displays multiple variables at different time scales.”
Dr. Heil said the availability of different sea-ice variables within the one application was also important in teasing out sea-ice conditions. For example, an area of interest could show 100% sea-ice concentration. However, including the sea-ice freeboard variable (height of sea ice above the water level), could identify areas of thicker or thinner ice within.
“An area of interest may be 100% covered in ice, and only the freeboard data will show whether it is freshly frozen over and very thin, or if it’s thick, multi-year ice that one would not want to venture in to,” she said.
The development team said the mapping platform could also be used by students to conceptualize climate variability, or to provide climate modelers with an accessible, visual means of comparing model outputs with actual observations.
“There are many ways to look at sea ice in Antarctica, but our tool brings together a diverse set of observations to explore Earth system characteristics and processes that are relevant to the Australian Antarctic Division and the Australian Southern Ocean science community,” Mr. Chua said.
“While people can view many of these variables in isolation, the power of our mapping tool is in the combination of variables and the ability to overlay them within an accessible interface.”
Paper: Southern Ocean related remote sensing datasets used by the Nilas Southern Ocean Mapping Platform., Australian Antarctic Data Centre (2023). DOI: 10.26179/9fcq-s321