Wednesday, 1 June 2022

Places on Earth where you can still see ice

Have you ever been fascinated by the fact that there are places on Earth where you can still see the ice?

Blog intro: We all know that the Earth is warming up. In fact, we have gone through 5 of the last 6 warmest years. But some places are so cold that they still have ice in them. Here are just some of them.

#1. Svalbard Global Seed Vault

Svalbard Global Seed Vault, located in Norway, is a seed bank that houses more than 10 million seeds from around the world.

#2. Antarctica

The continent of Antarctica is the coldest and windiest place on Earth. And there are still places where you can see ice.

#3. The Arctic Circle

The Arctic Circle is located in northern Scandinavia and marks the border between the North Pole and the rest of the planet.

#4. Greenland

Greenland is the world's largest island and is also the northernmost country in the world.

#5. The Himalayas

The Himalayas are a mountain range in the south Asia. There are more than 1,500 glaciers located here.

Monday, 9 May 2022

Comets and Origin of Life

Comets are bodies of ice, dust, and rock that orbit the Sun and exhibit a coma (or atmosphere) extending away from the Sun as a tail when they are close to the Sun. They have orbital periods that range from a few years to a few hundred or even thousands of years. Short-period comets have orbital periods of fewer than 200 years, and most of these orbit in the plane of the ecliptic in the same direction as the planets. Their orbits take them past the orbit of Jupiter at aphelion, and near the Sun at perihelion. 

Long-period comets have highly elongated or eccentric orbits, with periods longer than 200 years and extending to thousands or perhaps even millions of years. These comets range far beyond the orbits of the outer planets, although they remain gravitationally bound to the Sun. Another class of comets, called single-apparition comets, have a hyperbolic trajectory that sends them past the inner solar system only once, then they are ejected from the solar system. Before late 20th-century space probes collected data on comets, comets were thought to be composed primarily of ices and to be lone wanderers of the solar system. 

Now, with detailed observations, it is clear that comets and asteroids are transitional in nature, both in composition and in orbital character. Comets are now known to consist of rocky cores with ices around them or in pockets, and many have an organic-rich dark surface. Many asteroids are also made of similar mixtures of rocky material with pockets of ice. There are so many rocky/icy bodies in the outer solar system in the Kuiper belt and Oort Cloud that comets are now regarded as the most abundant type of bodies in the universe. There may be one trillion comets in the solar system, of which only about 3,350 have been cataloged. Most are long-period comets, but several hundred short-period comets are known as well. 

The heads of comets can be divided into several parts, including the nucleus; the coma, or gaseous rim from which the tail extends; and a diffuse cloud of hydrogen. The heads of comets can be quite large, some larger than moons or other objects including Pluto. Most cometary nuclei range between 0.3 and 30 miles (0.5–50 km) in diameter and consist of a mixture of silicate rock, dust, water ice, and other frozen gases such as carbon monoxide, carbon dioxide, ammonia, and methane. Some comets contain a variety of organic compounds including methanol, hydrogen cyanide, formaldehyde, ethanol, and ethane, as well as complex hydrocarbons and amino acids. Although some comets have many organic molecules, no life is known to exist on or be derived from comets. 

These organic molecules make cometary nuclei some of the darkest objects in the universe, reflecting only 2–4 percent of the light that falls on their surfaces. This dark color may actually help comets absorb heat, promoting the release of gases to form the tail. Cometary tails can change in length, and can be 80 times larger than the head when the comet passes near the Sun. As a comet approaches the Sun, it begins to emit jets of ices consisting of methane, water, and ammonia, and other ices. 

Modeling of the comet surface by astronomers suggests that the tails form when the radiation from the Sun cracks the crust of the comet and begins to vaporize the volatiles like carbon, nitrogen, oxygen, and hydrogen, carrying away dust from the comet in the process. The mixture of dust and gases emitted by the comet then forms a large but weak atmosphere around the comet, called the coma. The radiation and solar wind from the Sun causes this coma to extend outward away from the Sun, forming a huge tail. 

The tail is complex and consists of two parts. The first part contains the gases released from the comet forming an ion tail that gets elongated in a direction pointing directly away from the Sun and may extend along magnetic field lines for more than 1 astronomical unit (9,321,000 miles; 150,000,000 km). The second part is the coma, or thin atmosphere from which the tail extends, which may become larger than the Sun. Dust released by the comet forms a tail with a slightly different orientation, forming a curved trail that follows the orbital path of the comet around the Sun. Short-period comets originate in the Kuiper belt, whereas long-period comets originate in the Oort Cloud. 

Many comets are pulled out of their orbits by gravitational interactions with the Sun and planets or by collisions with other bodies. When these events place comets in orbital paths that cross the inner solar system, these comets may make close orbits to the Sun, and may also collide with planets, including the Earth. Several space missions have recently investigated the properties of comets. These include Deep Space 1, which flew by Comet Borrelly in 2001. Comet Borrelly is a relative small comet, about 5 miles (8 km) at its longest point, and the mission showed that the comet consists of asteroid-like rocky material, along with icy plains from which the dust jets that form the coma were being emitted. 

In 1999 the National Aeronautics and Space Administration (NASA) launched the Stardust Comet Sample Return Mission, which flew through the tail of comet Wild 2 and collected samples of the tail in a silica gel and returned them to Earth in 2006. Scientists were expecting to find many particles of interstellar dust or the extrasolar material that composes the solar nebula, but instead found little of this material; instead they found predominantly silicate mineral grains of Earthlike solar system composition. 

The samples collected revealed that comet Wild 2 is made of a bizarre mixture of material that includes some particles that formed at the highest temperatures in the early solar system, and some particles that formed at the coldest temperatures. To explain this, scientists have suggested that the rocky material that makes up the comet formed in the inner solar system during its early history, then was ejected to the outer bounds of the solar system beyond the orbit of Neptune, where the icy material was accreted to the comet. 

Calciumaluminum inclusions, which represent some of the oldest, highest temperature parts of the early solar system, were also collected from the comet. One of the biggest surprises was the capture of a new class of organic material from the comet tail. These organic molecules are more primitive than any on Earth and than those found in any meteorites; they are known as polycyclic aromatic hydrocarbons. Some samples even contain alcohol. 

These types of hydrocarbons, thought to exist in interstellar space, may yield clues about the origin of water, oxygen, carbon, and even life on Earth. Comets are rich in water, carbon, nitrogen, and complex organic molecules that originate deep in space from radiation-induced chemical processes. Many of the organic molecules in the coma of comets originated in the dust of the solar nebula at the time and location where the comets initially formed in the early history of the solar system. Comets are relatively small bodies that have preserved these early organic molecules in a cold, relatively pristine state. This has led many scientists to speculate that life may have come to Earth on a comet, early in the history of the planet. Clearly, comets both delivered organic material to the early Earth and also destroyed and altered organic material with the heat and shock from impacts. Numerical models of the impact of organic-rich comets with Earth show that some of the organic molecules could have survived the force of impact. 

The organic molecules in comets may be the source of the prebiotic molecules that led to the origins of life on Earth. Studies of the chemistry and origin of the atmosphere and oceans suggest that the entire atmosphere, ocean, and much of the carbon on Earth, including that caught up in carbonate rocks like limestone, originated from cometary impact. 

The period of late impacts of comets and meteorites on Earth lasted about a billion years after the formation of Earth, before greatly diminishing in intensity. Life on Earth began during this time, hinting at a possible link between the transport of organic molecules to Earth by comets, and the development of these molecules into life. 

The early atmosphere of Earth was also carbon dioxide–rich (much of which came from comets), however, and organic synthesis was also occurring on Earth. In addition to bringing organic molecules to Earth, the energy from impacts certainly destroyed much of any biosphere that attempted to establish itself on the early Earth. Even the late, very minor KT impact at Chicxulub had major repercussions for life on Earth. 

Certainly the early bombardment characterized by many very large impacts would have had a more profound effect on life. Any life that had established itself on Earth would need to be sheltered from the harsh surface environment, perhaps finding refuge along the deep sea volcanic systems known as black smokers, where temperatures remained hot but stable, and nutrients in the form of sulfide compounds were used by early organisms for energy.

Tuesday, 19 April 2022

What Are Conditions Like on the Outer Planets?

 Jupiter, Saturn, Uranus, and Neptune are the outer planets of our solar system. These are the four planets farthest from the Sun. The outer planets are much larger than the inner planets. Since they are mostly made of gases, they are also called gas giants.

The gas giants are mostly made of hydrogen and helium. These are the same elements that make up most of the Sun. Astronomers think that most of the nebula were hydrogen and helium. The inner planets lost these very light gases. In the inner solar system, the gases were too hot for the gravity of the inner planets to keep them. In the outer solar system, it was cold enough for the gravity of the planets to keep the colder slower-moving hydrogen and helium gas.

All of the outer planets have numerous moons. They also have planetary rings made of ice. Only the rings of Saturn can be easily seen from Earth. Jupiter is truly a giant! The planet has 318 times the mass of Earth and about 1400 times Earth’s volume. So Jupiter is much less dense than Earth. 

Because Jupiter is so large, it reflects a lot of sunlight. When it is visible, it is the brightest object in the night sky beside the Sun. Jupiter is quite far from the Earth. The planet is more than five times as far from the Sun as Earth. It takes Jupiter about 12 Earth years to orbit once around the Sun.  A Ball of Gas and Liquid

Since Jupiter is a gas giant, could a spacecraft land on its surface? The answer is no. There is no solid surface at all! Jupiter is made mostly of hydrogen, with some helium, and small amounts of other elements. The outer layers of the planet are gas. Deeper within the planet, the intense pressure condenses the gases into a liquid. Jupiter may have a small rocky core at its center.

A Stormy Atmosphere

Jupiter's atmosphere is made mostly of hydrogen and helium gas. There are also small amounts of other gases that contain hydrogen, like methane, ammonia, and water vapor. Astronomers think that clouds in the atmosphere are particles of water, ice, and compounds made of ammonia. Alternating cloud bands rotate around the planet in opposite directions. Colors in these cloud bands may come from complex organic molecules. 

The Great Red Spot, shown in the Figure above, is Jupiter's most noticeable feature. The spot is an enormous, oval-shaped storm. It can expand to be more than two times as wide as the entire Earth! Clouds in the storm rotate counterclockwise. They make one complete turn every six days or so. The Great Red Spot has been on Jupiter for at least 300 years. It may have been observed as early as 1664. It is possible that this storm is a permanent feature on Jupiter. No one knows for sure.

Jupiter’s Moons and Rings

Jupiter has lots of moons. As of 2012, we have discovered over 67 natural satellites of Jupiter. Four are big enough and bright enough to be seen from Earth using a pair of binoculars. These four moons were first discovered by Galileo in 1610. They are called the Galilean moons. The Figure below shows the four Galilean moons and their sizes relative to Jupiter’s Great Red Spot. These moons are named Io, Europa, Ganymede, and Callisto. 

The Galilean moons are larger than even the biggest dwarf planets, Pluto and Eris. Ganymede is the biggest moon in the solar system. It is even larger than the planet Mercury! Scientists think that Europa is a good place to look for extraterrestrial life. Europa is the smallest of the Galilean moons. The moon's surface is a smooth layer of ice. 

Scientists think that the ice may sit on top of an ocean of liquid water. How could Europa have liquid water when it is so far from the Sun? Europa is heated by differences in Jupiter’s gravity as Europa’s distance changes during an orbit. These tidal forces are so great that they stretch and squash its moon. This could produce enough heat for there to be liquid water. Various missions have been discussed to explore Europa, including the idea to have a probe melt deep down through the ice into the ocean. However, no such mission has yet been attempted.

In 1979, two spacecraft, Voyager 1 and Voyager 2 visited Jupiter and its moons. Photos from the Voyager missions showed that Jupiter has a ring system. This ring system is very faint, so it is very difficult to observe from Earth.

2: Saturn

Saturn, shown in the figure below, is famous for its beautiful rings. Saturn is the second largest planet in the solar system. Saturn’s mass is about 95 times Earth's mass. The gas giant is 755 times Earth’s volume. Despite its large size, Saturn is the least dense planet in our solar system. Saturn is actually less dense than water. This means that if there were a bathtub big enough, Saturn would float! In Roman mythology, Saturn was the father of Jupiter. Saturn orbits the Sun once about every 30 Earth years.

Saturn is the least dense planet in our solar system.

Saturn’s composition is similar to Jupiter's. The planet is made mostly of hydrogen and helium. These elements are gases in the outer layers and liquids in the deeper layers. Saturn may also have a small solid core. Saturn's upper atmosphere has clouds in bands of different colors. These clouds rotate rapidly around the planet. But Saturn has fewer storms than Jupiter.

Saturn’s Rings

Saturn's rings were first observed by Galileo in 1610. He didn't know they were rings and thought that they were two large moons. One moon was on either side of the planet. In 1659, the Dutch astronomer Christiaan Huygens realized that they were rings circling Saturn’s equator. The rings appear tilted. This is because Saturn’s rotation axis is tilted about 27 degrees from a line perpendicular to its orbit.

The Voyager 1 spacecraft visited Saturn in 1980. Voyager 2 followed in 1981. These probes sent back detailed pictures of Saturn, its rings, and some of its moons. The Cassini spacecraft has been in orbit around Saturn since 2004. From the Voyager and Cassini data, we learned that Saturn’s rings are made of mostly ice particles of different sizes with a little bit of dust. There are several gaps in the rings. The gaps result from gravitational interactions between the ring particles and Saturn’s moons that orbit outside the ring or by a small moon orbiting within the gap.

Saturn’s Moons

As of 2012, over 62 moons have been identified around Saturn. Only seven of Saturn’s moons are round. All but one is smaller than Earth’s moon. Some of the very small moons are found within the rings. All the particles in the rings are like little moons because they orbit around Saturn.

Saturn’s largest moon, Titan, is about one and a half times the diameter of Earth’s moon. Titan is even larger than the planet Mercury. Scientists are very interested in Titan. The moon has an atmosphere that is thought to be like Earth’s first atmosphere. This atmosphere was around before life developed on Earth. Like Jupiter's moon, Europa, Titan may have a layer of liquid water under a layer of ice. Scientists now think that there are lakes on Titan's surface. Don't take a dip, though. These lakes contain liquid methane and ethane instead of water! Methane and ethane are compounds found in natural gas.


Uranus is the 7th planet out from the Sun. Uranus' rings are almost perpendicular to the planet. Uranus, shown in the figure above, is named for the Greek god of the sky, the father of Saturn. Astronomers pronounce the name “YOOR-uh-nuhs.” Uranus was not known to ancient observers. The planet was first discovered with a telescope by the astronomer William Herschel in 1781.

Uranus is faint because it is very far away. Its distance from the Sun is 2.8 billion kilometers (1.8 billion miles). A photon from the Sun takes about 2 hours and 40 minutes to reach Uranus. Uranus orbits the Sun once about every 84 Earth years. An Icy Blue-Green Ball

Uranus is a lot like Jupiter and Saturn. The planet is composed mainly of hydrogen and helium, but Uranus has a higher percentage of “ices” than Jupiter and Saturn. These “ices” include water, ammonia, and methane. Uranus is also different because of its blue-green color. Methane gas absorbs red light so the reflected light gives Uranus a blue-green color. The atmosphere of Uranus has bands of clouds. These clouds are hard to see in normal light. The result is that the planet looks like a plain blue ball.

Uranus is the least massive outer planet. Its mass is only about 14 times the mass of Earth. Like all of the outer planets, Uranus is much less dense than Earth. Gravity is actually weaker than on Earth’s surface. If you were at the top of the clouds on Uranus, you would weigh about 10 percent less than what you weigh on Earth.

The Sideways Planet

All of the planets rotate on their axes in the same direction that they move around the Sun except for Venus and Uranus. While Venus rotates in the opposite direction, Uranus is tilted on its side. Its axis is almost parallel to its orbit. How did Uranus get this way? One possibility is that the planet was struck by a large planet-sized object as it was forming during the early days of the solar system.

Rings and Moons of Uranus

Uranus has a faint system of rings, as shown in the Figure below. The rings circle the planet’s equator. However, Uranus is tilted on its side. So the rings are almost perpendicular to the planet’s orbit. We have discovered 27 moons around Uranus. All but a few are named for characters from the plays of William Shakespeare. 4: Neptune

Neptune is shown in the Figure below. It is the eighth planet from the Sun. Neptune is so far away you need a telescope to see it from Earth. Neptune is the most distant planet in our solar system. It is nearly 4.5 billion kilometers (2.8 billion miles) from the Sun. One orbit around the Sun takes Neptune 165 Earth years.

Neptune has a great dark spot at the center-left and a small dark spot at the bottom center.

Scientists guessed Neptune's existence before it was discovered. Uranus did not always appear exactly where it should. They said this was because a planet beyond Uranus was pulling on it. This gravitational pull was affecting its orbit. Neptune was discovered in 1846. It was just where scientists predicted it would be! The planet was named Neptune for the Roman god of the sea.

Uranus and Neptune are often considered “sister planets.” They are very similar to each other. Neptune has slightly more mass than Uranus, but it is slightly smaller in size.

Extremes of Cold and Wind

Like Uranus, Neptune is blue. The blue color is mostly caused by the absorption of red light by methane in Neptune’s atmosphere. Neptune is not a smooth-looking ball like Uranus. The planet has a few darker and lighter spots. When Voyager 2 visited Neptune in 1986, there was a large dark-blue spot south of the equator. This spot was called the Great Dark Spot. When the Hubble Space Telescope photographed Neptune in 1994, the Great Dark Spot had disappeared. Another dark spot had appeared north of the equator.

Neptune's appearance changes due to its turbulent atmosphere. Winds are stronger than on any other planet in the solar system. Wind speeds can reach 1,100 km/h (700 mph). This is close to the speed of sound! The rapid winds surprised astronomers. This is because Neptune receives little energy from the Sun to power weather systems. It is not surprising that Neptune is one of the coldest places in the solar system. Temperatures at the top of the clouds are about –218°C (–360°F).

Neptune’s Rings and Moons

Like the other outer planets, Neptune has rings of ice and dust. These rings are much thinner and fainter than Saturn's. Neptune's rings may be unstable. They may change or disappear in a relatively short time.

Neptune has 13 known moons. Only Triton, shown in the Figure below, has enough mass to be round. Triton orbits in the direction opposite to Neptune's orbit. Because of this, scientists think Triton did not form around Neptune. The satellite may have been captured by Neptune’s gravity as it passed very close to Neptune.

·         The four outer planets — Jupiter, Saturn, Uranus, and Neptune — are all gas giants made mostly of hydrogen and helium. Their thick outer layers are gases and have liquid interiors.

·         All of the outer planets have lots of moons, as well as planetary rings made of dust and other particles.

·         Jupiter is the largest planet in the solar system. It has bands of different colored clouds, and a long-lasting storm called the Great Red Spot.

·         Jupiter has over 60 moons. The four biggest were discovered by Galileo, and are called the Galilean moons.

·         One of the Galilean moons, Europa, may have an ocean of liquid water under a layer of ice. The conditions in this ocean might be right for life to have developed.

·         Saturn is smaller than Jupiter but very similar to Jupiter. Saturn has a large system of beautiful rings.

·         Saturn’s largest moon, Titan, has an atmosphere similar to Earth’s atmosphere before life formed.

·         Uranus and Neptune were discovered using a telescope. They are similar to each other in size and composition. They are both smaller than Jupiter and Saturn, and also have more icy materials.

·         Uranus is tilted on its side, probably due to a collision with a large object in the distant past.

·         Neptune is very cold and has very strong winds. It had a large dark spot that disappeared. Another dark spot appeared on another part of the planet. These dark spots are storms in Neptune’s atmosphere.

Wednesday, 29 September 2021

Interviews with Key Informants: The Example of Morocco

One more piece of empirical evidence was collected for the qualitative fieldwork through interviews with key informants. In all five countries government officials and nongovernmental experts are well aware of the stress caused by changes in climatic conditions, and of the fact that climate change contributes to rural-urban migration flows even if today it is not the main driver of these flows. They also realize that in most cases, the lack of sufficiently ambitious and well-developed policies and programs contributes to the inability to propose concrete solutions and help to those most affected by climate change in rural areas. Many of the comments made by government officials and non-governmental experts in the various countries were similar so that rather than provide examples from all countries, it is probably more instructive to cover one country in slightly more depth. 

This is done in this section for Morocco because more respondents were either experts on migration or were conducting ongoing research on migration-related issues. Key informants in Morocco explained that migration was historically by men and driven by inequitable development in rural areas. The absence of networks in destination areas made women vulnerable to prostitution or slave labor, so they were less likely to migrate than men. Migrants migrated both internationally and internally, in that case principally to Casablanca, which continues to remain as a prime destination for rural migrants since the Greater Casablanca area alone still attracts around 15 percent of all national migration flows in the country. Today territorial units nearby Casablanca have also become preferred destinations for newcomers. 

This is for example the case of Ain Sebaa, Sidi Moumen, Moulay Rachid, Hay Hassani, Mohammedia city, and districts of Sidi Bernoussi and Hay Mohammadi. Migration to other cities has also picked up as rural migrants are searching for destinations closer to their homes. Key informants explained that three main features remain central to migratory flows irrespective of origin and destination locations. The first is the importance of networks which play a critical role in providing support to migrant families and in helping them to decide their destinations. A second key feature is the importance of the remittances sent by migrants, which are critical not only for household survival in rural areas but also for communities. In Tiznit for example, migrant associations are helping build two-thirds of the roads. Several informants also stated that migration facilitated women's empowerment in rural areas, as the women who remained in the countryside while their husbands were away working in the cities gained more independence and were also more likely to interact with their neighbors. A third important feature, especially in recent years, has been the role of climatic patterns in internal migration. 

Drastic changes in climatic conditions have led to an expansion of shantytowns. In Tafilelt for example, a fourth of the population has migrated due to climatic hazards that had affected agricultural production. Likewise, in the Draa region which has historically been an important center of trade but more recently has been experiencing frequent and longer droughts, out-migration has increased. In general, informants agree that the so-called Oasis belt is losing its population as people are becoming increasingly affected by the negative effects of droughts. Outgoing migration is primarily stemming from the water crisis that Morocco is experiencing. Six of our respondents mentioned water as a major issue, in part due to more droughts, but also with flooding in some areas. 

For example, the Tafilalt region, one of the most important oasis regions in the country, has suffered from severe droughts and flooding which in turn have undermined oasis agriculture. While droughts used to occur every four to five years, they now occur every two years. Climatic hazards are also leading to severe desertification in the Sahara region. Rising seawater levels are also a concern, among others in Saadia where tourism may have contributed to destroying plant life and consequently making the land vulnerable. A respondent suggested that 60 percent of Saadi may soon be underwater. These severe climatic conditions have had a large impact on rural populations, with farmers experiencing increased water scarcity with no access to water reserves. Women have to travel much further away to get water. 

Some respondents were convinced that agricultural yields will fall by 20 percent in 20 years, which drive more migrants from rural areas toward urban centers. Life in the cities will then become difficult for both locals and migrants. Many respondents mentioned ongoing housing and employment crises in urban areas. As locals and migrants compete for survival, the integration will become a major problem and economic discrimination will rise, as may black markets and the informal economy. In large cities such as Casablanca, many migrants are already found to be living in shantytowns. The pressures of living in cities along with influences from urban lifestyles have also been weakening social structures between migrants and their families which may have severe consequences for those still living in Morocco’s rural areas. 

In recognition of these challenges, respondents explained that the Moroccan government launched initiatives at both the national and local levels. One such initiative is a higher focus on rural development programs, among others, through the Human Development Initiative (HDI) which is designed to target vulnerable populations in both rural and urban areas. At the local level, the government is also conducting awareness programs to inform people about climate change. The objective is to teach people about conservation and preservation of water resources, disaster preparedness to limit the negative effects of droughts, and different irrigation schemes to encourage the agricultural sector to become independent of water resources. 

Climate change has also been included as a key component in other initiatives such as Morocco Green and the Communal Development Plan. There is also an Energy Strategy Plan being initiated, and work is ongoing toward an insurance plan named ‘Natural Catastrophe Insurance.’ Active research programs are also ongoing in a few universities. Despite these initiatives, respondents perceived some fatalism, with many believing that everything is happening because of Allah’s will. And at times government programs may contribute to the issues. One respondent mentioned a dam that instead of stopping flooding drained water resources from the ground, leading to poor water quality and affecting surrounding palm trees.

Adverse Weather Trends

Adverse weather trends such as increased flooding and droughts shape the decisions to migrate made by household and individuals. Climate change is widely perceived to reduce crop yields and livestock production, decrease water availability, reduce fishing populations, and limit opportunities in rural areas that depend heavily on agriculture. The goal of this chapter was to contribute to a better understanding of the relationships between climate change, environmental degradation, deterioration of agriculture, and human mobility, through an exploration of the attitudes of rural residents and urban migrants in our five focus countries. Rural residents use a range of coping mechanisms to survive, ranging from eating less and borrowing money to selling livestock and other assets. 

Remittances are also important for survival, and when this source of income is insufficient, additional household members are forced to migrate to other areas in search of better opportunities. Overall, while in some countries such as Egypt and to some extent Morocco, there is a perception that migration opens up new opportunities, in other countries such as Syria, for many migrants migration may be a strategy of last resort than a real choice. While such differences between countries seem to emerge from the qualitative fieldwork and tend to also be supported by quantitative household survey data, of course, individual situations remain highly household and area-specific within each of the five countries. 

The qualitative work also suggests that for urban migrants, the arduous task of obtaining a job is further hindered by corruption and fierce competition with locals for limited employment opportunities. Social dislocation is a risk, with many migrants feeling inferior, alienated, and different in their new urban environs. Many face job discrimination, harassment, and exploitation at the hands of their supervisors and would-be employers. Poor housing conditions, rising food and rent prices, and the obligation to send remittances back home place substantial pressure on urban migrants. Yet, these coexist alongside some benefits. 

For example, migrants appreciate the independence, social outlets, and opportunities that urban life has to offer. A number of suggestions were made by households as well as migrants about the types of programs that could be of help to them, in both urban and rural areas. It is not the place in this chapter to comment on whether such recommendations are appropriate, or even feasible to implement by governments. In order to come up with such an assessment, a much more detailed analysis of the types of programs proposed, their cost, and their benefits, would be required. 

But what does emerge from the interviews with key informants is that while government officials and nongovernmental experts are aware of the consequences of climate change and extreme weather events for the population, they also recognize that the extent to which governments are dealing with these issues today is limited. This is a finding that is also emerging from other chapters in this study, in that both the community level responses and government programs and policies not only to cope with weather shocks but also to adapt to climate change, remain insufficient.

Tuesday, 25 May 2021

Forest in Trouble

As the 1990s progressed, it became clear to those of us in public health that a wave of infectious diseases was striking humans and many other forms of life. Humans faced multi-drug-resistant tuberculosis, Ebola, HIV, and dozens of other new pathogens. Crops were becoming infested with insects and infected with emerging viruses. Dolphins, whales, and seals were suffering from measles-like viruses, while fish were going belly up en masse with increasing frequency. Even trees were in trouble. 

Throughout the 1990s, I’d been trying to forge a new synthesis that would explain how a changing world could breed a wave of epidemics. I had begun my intellectual exploration into health and global change by gazing at a diagram that hangs in frames on the walls of public health offices nationwide. The diagram consists of three interlocking circles, emblazoned with the letters A, H, and E. It is known as a Venn diagram, and it holds the key to epidemiology, the study of epidemics. 

The circle labeled A represents the agent—meaning the bacterium, virus, parasite, or fungus that can, if conditions are right, infect a person, plant, or animal. The second circle, H, represents the host—the organism that becomes infected with the agent. The third circle, E, represents the environment—the external conditions that determine whether the agent will invade a host. The same three factors—agent, host, and environment—control whether people develop other diseases as well. The take-home lesson is that there are most often multiple causes for any one person’s sickness. 

The agent causing tuberculosis, for example, is the bacterium Mycobacterium tuberculosis. But even if M. tuberculosis is present, the disease won’t always develop. It will be more likely to occur if the host is weakened, perhaps by malnutrition or an HIV infection, and if conditions are ripe for transmission. Ideal tuberculosis-transmitting conditions occur in close quarters, such as those in the gold mines of South Africa or 1980s-era crack houses or prisons in New York City, where infected people cough profusely into common airspace. A host with a strong immune system living in a healthy environment can usually fight off the infection by surrounding the slow-growing bacteria with immune cells, effectively quarantining them and preventing the disease. But a weak host in close quarters is more likely to be infected and have trouble fighting the disease. 

This framework of agent, host, and environment, I’d realized, could be adapted to assess the impacts of global change. When global change is considered, ecosystems are the host. This analogy works on several levels. First, like the human immune system, both land-and ocean-based ecosystems have components that fight disease. In the immune system, antibodies stun invading pathogens, and white blood cells devour them. In terrestrial (land-based) ecosystems, birds of prey, like the spotted owls of the U.S. Pacific Northwest, eat rodents that can carry Lyme-disease-infected ticks, hantavirus, and bubonic plague. In marine (ocean-based) ecosystems, baleen whales and oysters filter-feed on algae and animal plankton, preventing the plankton from overgrowing into harmful algal blooms. 

Second, just as a host is influenced by its environment, every ecosystem is influenced by the global environment. This includes the conditions in the lower atmosphere (troposphere), the upper atmosphere (stratosphere), the biosphere, the ice cover (cryosphere), and the world ocean. Even disregarding climate change, humans have made huge changes to the global environment. By using chlorofluorocarbons and related chemicals in our air conditioners and antiperspirants, we’ve damaged the ozone layer in the stratosphere that protects all land-based life from the sun’s damaging ultraviolet rays. 

By overfishing, we’ve decimated once-abundant populations of cod and many other species. By unwittingly releasing dangerous synthetic chemicals that act like hormones in animal bodies, we’ve altered the fate of countless species. The list of disturbances goes on. Climate change portends larger changes by affecting the viability of entire ecosystems. Persistent warming can kill off vegetation, turning grasslands into deserts, as it did when a changing climate transformed the Sudanese Sahara 5,500 years ago from a semiarid grassland suitable for grazing sheep to the bone dry desert it is today. 

Warming seas make it harder for coral to reproduce, contributing to the coral bleaching events that are destroying reefs worldwide. Warmer and more variable weather can enable insects, including crop pests, finally, the analogy works because human civilization is disrupting the functioning of the ecosystems that supply us with healthy food, clean air, and pure water, just as pathogenic microbes disrupt the functioning of the host’s body, upon whom they rely for life support. 

Human civilizations are also disrupting the global environment. The overlapping circles of this Venn diagram represent these interactions. All of our social structures—our economy, our legal system, our energy system—influence both ecosystems and the global environment. That means that the agent in this analogy is usThis Venn diagram is useful in part because it offers an easy-to-grasp framework that illustrates how complex real-world systems work. 

Conditions in a host, whether human or ecosystem, must be conducive for an agent, be it microbe or human society, to flourish. And when conditions are such that the agent, host, and environment are all disturbed, a small problem can turn into a big one. A cold virus invading the throat of an overstressed person can cause days of sickness; a wildlife disease invading a disturbed and weakened ecosystem can spread and become an epidemic.

Wednesday, 30 September 2020

Earth, internal structure of Earthquakes and volcanoes

 Earth, the internal structure of Earthquakes, and volcanoes are manifestations of processes at work deep within Earth. These processes in turn are evidence of Earth’s internal structure, models of which have undergone considerable evolution in the 20th century. On a large scale, the internal features of Earth may be categorized as follows:

1. Core. This is the innermost layer of Earth, a dense, approximately spherical mass of very hot rock that accounts for roughly one-third of the planet’s mass and one-sixth of its volume. The core is divided into a solid inner core and a liquid outer layer.

2. Mantle. The mantle, the thick layer of rock surrounding the core, contains about two-thirds of Earth’s mass and more than four-fifths of its volume. An outer layer of the mantle is called the asthenosphere and is involved closely with driving plate tectonics. There is also a division within the upper and lower mantle based on mineral structure.

3. Crust. The crust, or surface layer, of Earth, is very thin compared to the mantle and core (five to 80 miles [8 to 129 km] thick) and accounts for only a tiny fraction of Earth’s total mass and volume. The crust floats on the asthenosphere by a process called isostasy, in which the relatively lightweight rocks of the crust are supported by the denser rocks below. The crust is divided into several individuals, rigid plates that interact with one another through various processes, generating earthquakes and volcanic activity. The crust contains many faults that produce numerous earthquakes.

Earthflow - an earthflow is a type of mass movement. It is a viscous flow of saturated, fine-grained materials that move downslope at speeds ranging from barely perceptible up to about 10 miles per hour (about 0.1 m/sec). Materials susceptible to earthflow include clay, fine sand and silt, and fine-grained pyroclastic material (primarily ash). 

The velocity and distance of the earthflow are controlled by water content, with faster and longer movements through higher water content. Some earth flows may continue to move for years. Earth flows normally begin when the water content increases either through rain, melting (normal heating or volcanic eruption), or liquefaction during an earthquake. Shaking from an earthquake may also initiate flow in saturated soil. The flows tend to bulge in the middle as they move, which in turn channels more fluid to the middle while the edges dry out. Earth flows will stop moving when the water content drops.

Earthquake hazard. An earthquake hazard is considered to be any of the damaging effects and processes of an earthquake that may affect the normal activities of people. Examples of earthquake hazards include surface faulting, ground shaking, landslides, liquefaction, slumping, fissures, avalanches, tsunamis, and seiches, among others.

Earthquake light - This phenomenon consists of a peculiar glow that sometimes is reportedly seen in the sky during earthquakes. What causes earthquake light is uncertain, but it has been suggested that methane escaping from underground during earthquakes is ignited somehow and burns near the surface, giving off light.

Earthquake risk - Earthquake risk is the probable damage to buildings, roads, services, and other infrastructure and the number of people that are expected to be killed or injured during an earthquake of a size in a location. Earthquake risk is a probabilistic model for a specific seismic event. It varies considerably with each area depending upon population and emergency readiness.

Earthquake swarm - Many earthquakes preceding a volcanic eruption. As magma moves upward in the crust, it pushes rock out of the way. It forces open cracks in the rock. Each break results in a small earthquake. These earthquakes are typical of magnitudes of 4 or less, but some larger earthquakes are possible. There can be hundreds to thousands of earthquakes in such swarms. volcanologists use this kind of seismic activity to predict eruptions. The correlation is not foolproof. Many earthquake swarms do not foretell a coming eruption but rather just the movement of magma.