From September 2019 to January 2020, Australia experienced continuous record-breaking hot weather and severe drought, triggering forest fires that burned for more than four months. Many people were killed and more than 1 billion wild animals were affected. The fire also destroyed nearly 6,000 buildings and brought smog over many cities, causing serious pollution of the air, soil and drinking water.

On 20 July 2021, heavy rains hit the central and northern Henan province, among which Zhengzhou experienced extremely heavy rains, with rainfall exceeding 200mm in one hour. The floods caused by heavy rains resulted in more than 300 deaths in Henan, affecting more than 14 million people, and the direct economic loss exceeded RMB100 billion.

In August 2021, Hurricane Ida made landfall in Louisiana, a southern state in the United States, causing several deaths and power outages affecting millions of people. Later on, Ida torn through the northeastern region of the United States with heavy rains, floods and tornadoes, and caused at least 43 deaths and immeasurable losses.

In recent years, the frequency of extreme weather all over the world is increased. The consensus in the scientific community is that it is closely related to climate change, i.e. global warming.

More evidence of global warming

Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental organization affiliated to the United Nations that specializes in climate change caused by human activities. Established in 1988, IPCC and thousands of outstanding scientists around the world have finished five assessments of climate change.

The sixth climate assessment report was released on 9 August, 2021. It received extensive attention from domestic and foreign media upon release, because everyone has realized that global climate change has become a problem that all mankind has to pay attention to and address.

The first working group report released from the sixth assessment cycle of the IPCC is called "Climate Change 2021: The Physical Science Basis". The report pointed out it is remarkable that human activities are leading to climate warming. At present, the average temperature of the earth has risen by 1.1°C compared to that before the industrial revolution (1850). Undoubtedly, in the past 2000 years, human activities are responsible for the warming of the atmosphere, oceans and land.

Image source: IPCC

The report pointed out that humans emit greenhouse gases through the burning of fossil fuels, causing global warming. In addition, the report also projected five greenhouse gas emission scenarios in the future, namely "extremely low, low, medium, high, and extremely high". According to the simulation results of the aforementioned five emission scenarios, no matter which, the global temperature will all increase by 1.5°C compared to that before the industrial revolution in the last 20 years. Only under the very low emission scenario, by the end of this century, global warming can be controlled at 1.5°C. This means that the world needs to achieve carbon neutrality around 2055.

Melting glaciers and exposed frozen soils

Zhai Panmao, a researcher at the Chinese Academy of Meteorological Sciences and co-chair of Working Group 1 of the IPCC Sixth Assessment Report, commented at the media interview held by the China Meteorological Administration: "The profound impact of human activities on the climate system has expanded from the atmosphere to oceans, cryosphere, and terrestrial biospheres. Human activity impact have been found in ocean acidification, rise of global sea level, retreating global glacier, shrinkage of Arctic Ocean ice extent, declining of Northern Hemisphere spring snow cover, Greenland ice cap melting, and growth period extension in temperate zone of north earth."

In August 2019, local icelanders held a "funeral" for Okjökull glacier, the first glacier in Iceland to disappear due to climate change. Scientists warn that hundreds of other glaciers on this subarctic island are facing the same fate.

1986 (left) and 2019 (right), Okjökull glacier comparison

Image source: NASA

At that time, the Northern Hemisphere was experiencing the hottest summer on record, and regions of western Iceland that was once covered by the Okjökull glacier, now only has barren land. People put a bronze plaque on a bare rock to alert the world of the serious impact of the irreversible global climate change on the ecological environment.

Globally, the melting rate of glaciers almost doubled in the past five years. Storage of fresh water in glacier has plummeted changing the structure of the surrounding ecosystem. For example, the permafrost in the Arctic has slowly begun to melt. In Siberia and northern Canada, this sudden "thaw" caused the land to sink, and the oldest and deepest permafrost layer was exposed to warm air for the first time after hundreds or even thousands of years.

Permafrost covers 24% of the earth’s land surface, and its composition varies depending on the local conditions. For most of human history, permafrost has reserved animals, plants, and microorganisms within. It is estimated that the permafrost stores approximately 1,600 billion tons of carbon, more than twice the carbon content of the atmosphere. As the global temperature increases, the permafrost is melting faster and faster, and many bacteria and archaea will "wake up" to further produce large amounts of carbon dioxide, methane and other greenhouse gases.

The awakened microbe, the unknown future

In addition to the known impact on climate change that might be brought by microorganisms in permafrost, scientists are even more worried about the threats to human health from those wakening microorganisms in permafrost.

Bacillus anthracis spores are extremely cold-resistant, and they can survive after centuries of freezing. In 2016, the permafrost in Siberia melted and released Bacillus anthracis spores that were "frozen" 75 years ago. The anthrax outbreak caused the death of more than 200,000 reindeer and one child.

In addition, viruses that we considered extinct may also appear in our environment in new ways. For example, in Alaska, a newly discovered orthopox virus (similar to variola virus) that can cause skin breakage has appeared and disappeared twice in the past five years. This new virus may be spread through animal-human contact, but its origin is still unknown.

Microbes that scientists are completely unfamiliar with may represent a brand new threat.

In June 2021, scientists from Russia published a study in the journal Current Biology. The report pointed out that scientists recovered a multicellular invertebrate rotifer (bdelloid rotifer) from the permafrost of Northeastern Siberia. It used to live in about 24,000 years ago. After thawing, these ancient rotifers not only successfully resurrected, but also reproduced asexually in the laboratory.

Rotifer recovered from the permafrost

Image source: Current Biology

Genetic analysis revealed that this ancient rotifer is a new species belonging to the genus Adineta and is most closely related to the modern Adineta vaga rotifer found in Belgium. Scientists still don't know what impact this new rotifer will have on our environment once it awakens on a large scale in nature.

Apparently, the warmer the Arctic, the stranger it will become. As microorganisms are recovering from the permafrost, we must adopt stronger biological monitoring measures to protect the residents at the Poles and other regions. But more importantly, we must control global warming and slow down the melting of permafrost. Otherwise, one day, the next "super virus" will quietly resurrect somewhere on earth.

Reference:
A living bdelloid rotifer from 24,000-year-old Arctic permafrost. Lyubov Shmakova et al. Current Biology. 2021. 31, R697–R713

Other sources:
IPCC, Institute of Earth Environment at Chinese Academy of Science, People.cn,  China Meteorological Administration, NASA, Scientific American, Current Biology