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GS Paper: GS1-14.Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.,

  • Recovery of Ozone Layer achieves significant milestone

    The concentration of ozone-depleting substances in the atmosphere has reduced to reach a significant milestone this year.

    What is Ozone and Ozone Layer?

    • An ozone molecule consists of three oxygen atoms instead of the usual two (the oxygen we breathe, O2, makes up 21% of the atmosphere).
    • It only exists in the atmosphere in trace quantities (less than 0.001%), but its effects are very important.
    • Ozone molecules are created by the interaction of ultra-violet (UV) radiation from the Sun with O2 molecules.
    • Because UV radiation is more intense at higher altitudes where the air is thinner, it is in the stratosphere where most of the ozone is produced, giving rise to what is called the ‘ozone layer’.
    • The ozone layer, containing over 90% of all atmospheric ozone, extends between about 10 and 40km altitude, peaking at about 25km in Stratosphere.

    Why need Ozone Layer?

    • The ozone layer is very important for life on Earth because it has the property of absorbing the most damaging form of UV radiation, UV-B radiation which has a wavelength of between 280 and 315 nanometres.
    • As UV radiation is absorbed by ozone in the stratosphere, it heats up the surrounding air to produce the stratospheric temperature inversion.

    What is Ozone Hole?

    • Each year for the past few decades during the Southern Hemisphere spring, chemical reactions involving chlorine and bromine cause ozone in the southern polar region to be destroyed rapidly and severely.
    • The Dobson Unit (DU) is the unit of measure for total ozone.
    • The chemicals involved ozone depletion are chlorofluorocarbons (CFCs for short), halons, and carbon tetrachloride.
    • They are used for a wide range of applications, including refrigeration, air conditioning, foam packaging, and making aerosol spray cans.
    • The ozone-depleted region is known as the “ozone hole”.

    Tropical Ozone Hole

    • According to the study, the ozone hole is located at altitudes of 10-25 km over the tropics.
    • This hole is about seven times larger than Antarctica, the study suggested.
    • It also appears across all seasons, unlike that of Antarctica, which is visible only in the spring.
    • The hole has become significant since the 1980s. But it was not discovered until this study.

    What caused an ozone hole in the tropics?

    • Studies suggested another mechanism of ozone depletion: Cosmic rays.
    • Chlorofluorocarbon’s (CFC) role in depleting the ozone layer is well-documented.
    • The tropical stratosphere recorded a low temperature of 190-200 Kelvin (K).
    • This can explain why the tropical ozone hole is constantly formed over the seasons.

    Significance of the finding

    • The tropical ozone hole, which makes up 50 percent of Earth’s surface, could cause a global concern due to the risks associated with it.
    • It is likely to cause skin cancer, cataracts and other negative effects on the health and ecosystems in tropical regions.

    Try this PYQ

    Q.Consider the following statements:

    Chlorofluorocarbons, known as ozone-depleting substances are used:

    1. In the production of plastic foams
    2. In the production of tubeless tyres
    3. In cleaning certain electronic components
    4. As pressurizing agents in aerosol cans

    Which of the statements given above is/are correct?

    (a) 1, 2 and 3 only

    (b) 4 only

    (c) 1, 3 and 4 only

    (d) 1, 2, 3 and 4

     

    [wpdiscuz-feedback id=”dl4j162prv” question=”Please leave a feedback on this” opened=”1″]Post your answers here[/wpdiscuz-feedback]

     

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  • What are Cloudbursts? Why are they rising across India?

    Over 20 people have been killed in destruction caused by cloudbursts and flash floods in different parts of Himachal Pradesh and Uttarakhand over the last three days.

    What are Cloudbursts?

    • A cloudburst is a localised but intense rainfall activity.
    • Short spells of very heavy rainfall over a small geographical area can cause widespread destruction, especially in hilly regions where this phenomenon is the most common.
    • Not all instances of very heavy rainfall, however, are cloudbursts.
    • A cloudburst has a very specific definition: Rainfall of 10 cm or more in an hour over a roughly 10 km x 10-km area is classified as a cloudburst event.
    • By this definition, 5 cm of rainfall in a half-hour period over the same area would also be categorized as a cloudburst.

    How is it different from normal rainfall?

    • To put this in perspective, in a normal year, India, as a whole, receives about 116 cm of rainfall over the entire year.
    • This means if the entire rainfall everywhere in India during a year was spread evenly over its area, the total accumulated water would be 116 cm high.
    • There are, of course, huge geographical variations in rainfall within the country, and some areas receive over 10 times more than that amount in a year.
    • But on average, any place in India can be expected to receive about 116 cm of rain in a year.
    • During a cloudburst event, a place receives about 10% of this annual rainfall within an hour.

    How common are cloudbursts?

    • Cloudbursts are not uncommon events, particularly during the monsoon months.
    • Most of these happen in the Himalayan states where the local topology, wind systems, and temperature gradients between the lower and upper atmosphere facilitate the occurrence of such events.
    • However, not every event that is described as a cloudburst is actually, by definition, a cloudburst.
    • That is because these events are highly localized.
    • They take place in very small areas which are often devoid of rainfall measuring instruments.

    Why are they so destructive?

    • The consequences of these events, however, are not confined to small areas.
    • Because of the nature of terrain, the heavy rainfall events often trigger landslides and flash floods, causing extensive destruction downstream.
    • This is the reason why every sudden downpour that leads to destruction of life and property in the hilly areas gets described as a “cloudburst”, irrespective of whether the amount of rainfall meets the defining criteria.
    • At the same time, it is also possible that actual cloudburst events in remote locations aren’t recorded.

    Can cloudbursts be forecasted?

    • The India Meteorological Department forecasts rainfall events well in advance, but it does not predict the quantum of rainfall — in fact, no meteorological agency does.
    • The forecasts can be about light, heavy, or very heavy rainfall, but weather scientists do not have the capability to predict exactly how much rain is likely to fall at any given place.
    • Additionally, the forecasts are for a relatively large geographical area, usually a region, a state, a meteorological sub-division, or at best a district.
    • As they zoom in over smaller areas, the forecasts get more and more uncertain.
    • Theoretically, it is not impossible to forecast rainfall over a very small area as well, but it requires a very dense network of weather instruments and computing capabilities that seem unfeasible with current technologies.
    • As a result, specific cloudburst events cannot be forecast. No forecast ever mentions a possibility of a cloudburst.
    • But there are warnings for heavy to very heavy rainfall events, and these are routinely forecast four to five days in advance.
    • Possibility of extremely heavy rainfall, which could result in cloudburst kind of situations, are forecast six to 12 hours in advance.

    Are cloudburst incidents increasing?

    • There is no long-term trend that suggests that cloudbursts, as defined by the IMD, are rising.
    • What is well established, however, is that incidents of extreme rainfall, as also other extreme weather events, are increasing — not just in India but across the world.
    • While the overall amount of rainfall in India has not changed substantially, an increasing proportion of rainfall is happening in a short span of time.
    • That means that the wet spells are very wet, and are interspersed with prolonged dry spells even in the rainy season.
    • This kind of pattern, attributed to climate change, does suggest that cloudburst events might also be on the rise.

     

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  • What is causing Arctic Amplification?

    Finnish researchers have found that the Arctic is heating four times faster than the rest of the planet.

    Arctic is warming faster

    • The warming is concentrated in the Eurasian part of the Arctic, where the Barents Sea north of Russia and Norway is warming at an alarming rate — seven times faster than the global average.
    • Other studies indicate that the Arctic amplification is four times the global rate.

    What is Arctic Amplification?

    • Global warming has hastened due to anthropogenic forces or human activities since pre-industrial times and has increased the planet’s average temperature by 1.1 degrees Celsius.
    • While changes are witnessed across the planet, any change in the surface air temperature and the net radiation balance tend to produce larger changes at the north and south poles.
    • This phenomenon is known as polar amplification; these changes are more pronounced at the northern latitudes and are known as the Arctic amplification.

    What causes amplification?

    • Among the many global warming-driven causes for this amplification, the ice-albedo feedback, lapse rate feedback, water vapour feedback and ocean heat transport are the primary causes.
    • Sea ice and snow have high albedo (measure of reflectivity of the surface), implying that they are capable of reflecting most of the solar radiation as opposed to water and land.
    • In the Arctic’s case, global warming is resulting in diminishing sea ice.
    • As the sea ice melts, the Arctic Ocean will be more capable of absorbing solar radiation, thereby driving the amplification.
    • The rate at which the temperature drops with elevation i.e. lapse rate decreases with warming.
    • Studies show that the ice-albedo feedback and the lapse rate feedback are responsible for 40% and 15% of polar amplification respectively.

    What do the previous studies say?

    • The extent of Arctic amplification is debated, as studies show various rates of amplification against the global rate.
    • Studies have shown that the Arctic was warming at twice the global rate prior to the beginning of the 21st century.
    • Already the Arctic surface air temperature has likely increased by more than double the global average over the last two decades.

    What are the consequences of Arctic warming?

    • The causes and consequences of Arctic amplification are cyclical — what might be a cause can be a consequence too.
    • The Greenland ice sheet is melting at an alarming rate, and the rate of accumulation of sea ice has been remarkably low since 2000.
    • This is also marked by young and thinner ice replacing the old and thicker ice sheets.
    • Greenlandic ice sheet holds the second largest amount of ice, after Antarctica, and therefore it is crucial for maintaining the sea level.
    • In 2019, this was the single biggest cause for the rise in the sea level, about 1.5 metres.

    Visible impacts

    • If the sheet melts completely, the sea level would rise by seven metres, capable of subsuming island countries and major coastal cities.
    • The warming of the Arctic Ocean and the seas in the region, the acidification of water, changes in the salinity levels, are impacting the biodiversity, including the marine species and the dependent species.
    • The warming is also increasing the incidence of rainfall which is affecting the availability and accessibility of lichens to the reindeer.
    • The Arctic amplification is causing widespread starvation and death among the Arctic fauna.
    • The permafrost in the Arctic is thawing and in turn releasing carbon and methane which are among the major greenhouse gases responsible for global warming.
    • Experts fear that the thaw and the melt will also release the long-dormant bacteria and viruses that were trapped in the permafrost and can potentially give rise to diseases.

    What is the impact on India?

    • In recent years, scientists have pondered over the impact the changing Arctic can have on the monsoons in the subcontinent.
    • The link between the two is growing in importance due to the extreme weather events the country faces, and the heavy reliance on rainfall for water and food security.
    • A study says that reduced sea ice in the Barents-Kara sea region can lead to extreme rainfall events in the latter half of the monsoons — in September and October.
    • The changes in the atmospheric circulation due to diminishing sea ice combined with the warm temperatures in the Arabian Sea contribute to enhanced moisture and drive extreme rainfall events.

    Steps taken by India

    • In 2014, India deployed IndARC, India’s first moored-underwater observatory in the Kongsfjorden fjord, Svalbard.
    • It aims to monitor the impact of the changes in the Arctic Ocean on tropical processes such as the monsoons.

     

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  • What is a Carbon Market, and why does India want to create one?

    The Bill to amend the Energy Conservation Act, 2001 seeks to establish a domestic carbon market and facilitate trade in carbon credits.

    What are Carbon Credits?

    • Carbon credits are measurable, verifiable emission reductions from certified climate action projects.
    • These projects reduce, remove or avoid greenhouse gas (GHG) emissions.
    • But they also bring a whole host of other positive benefits, for example, they empower communities, protect ecosystems, restore forests or reduce reliance on fossil fuels.
    • Projects must adhere to a rigorous set of criteria to pass verification by third-party agencies and a review by a panel of experts at a leading carbon offset standard.
    • After an organization or an individual buys a carbon credit, the credit is permanently retired so it can’t be reused.

    What are Carbon Markets?

    • Carbon markets are regulatory structures that allow, in particular, oil and gas-intensive companies or heavy industry (or, in the case of COP25, countries) to reduce their economic footprint through a series of incentives.
    • The idea behind this system is that the most polluting countries can purchase the right to pollute more from countries that have not reached their emissions limits.
    • The 1997 Kyoto Protocol turned polluting emissions into a commodity.
    • For example, the European Union Emissions Trading System (EU ETS) is the largest in the world and has been in operation since 2015.

    How is the concept evolved?

    • When the world evolved the ‘clean development mechanism’ (CDM) after the Kyoto Protocol agreement of 1997 as companies in the developing world could put up projects.
    • These include renewable energy or afforestation — that helped reduce carbon dioxide emissions, and earn ‘credits’ that could be sold in the market.
    • It was expected that these credits would be bought by the developed countries that had committed to emissions cuts under the Protocol.
    • Thus emerged the CDM market, aka ‘compliance market’. Alongside, environmentally conscious entities also started buying these carbon credits (or offsets) — the ‘voluntary market’.

    What is the status now?

    • This system functioned well for a few years.
    • But the market collapsed because of the lack of demand for carbon credits.
    • As the world negotiated a new climate treaty in place of the Kyoto Protocol, the developed countries no longer felt the need to adhere to their targets under the Kyoto Protocol.
    • A carbon market was envisaged to work under the successor Paris Agreement, but its details are still being worked out.

    Global successes

    • Domestic or regional carbon markets are already functioning in several places, most notably in Europe, where an emission trading scheme (ETS) works on similar principles.
    • Industrial units in Europe have prescribed emission standards to adhere to, and they buy and sell credits based on their performance.
    • China, too, has a domestic carbon market.

    Mechanism in India

    • A similar scheme for incentivizing energy efficiency has been running in India for over a decade now.
    • This BEE scheme, called- Perform, Achieve and Trade (PAT) Scheme allows units to earn efficiency certificates if they outperform the prescribed efficiency standards.
    • The laggards can buy these certificates to continue operating.

    What does new Amendment seeks to bring?

    • The new carbon market that is proposed to be created through this amendment to the Energy Conservation Act, would be much wider in scope.
    • Although the details of this carbon market are not yet known, it is likely to be on the lines of the European ETS, facilitating the buying and selling of carbon credits.

     

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  • Earth has recorded its shortest day since the 1960s- why?

    On June 29, the Earth completed one full spin — a day — in 1.59 milliseconds less than its routine 24 hours. It was the shortest day recorded since the 1960s.

    Note: A millisecond is one-thousandth of a second.

    Earth spinning faster

    • While the Earth has been completing its rotations faster in recent years, when looked at over a much longer period of time, our planet is actually spinning slower.
    • Every century, the Earth takes a few milliseconds longer to complete one rotation — and on average, days are actually getting longer.
    • So, 1.4 billion years ago, a day would have ended in less than 19 hours,

    How did scientists find that?

    • Scientists got to know by using precise atomic clocks to measure the Earth’s rotational speed.

    Why are days getting shorter these days?

    • Scientists aren’t entirely sure.
    • Something has changed and changed in a way we haven’t seen since the beginning of precise radio astronomy in the 1970s.

    Factors attributing Earth’s Spin

    (1) Tidal Braking

    • The research attributed the larger trend of the Earth’s slower spin mostly to the gravitational pull of the Moon, which causes tidal friction and slows down the Earth’s rotations.

    (2) Climate change-induced surface variations

    • Melting ice sheets in Greenland and Antarctica
    • Changes in ocean circulation

    (3) Geomorphic factors

    • Movements in the planet’s inner molten core
    • Seismic activity
    • Wind speed, and shifting atmospheric gases

    (4) Chandler wobble phenomenon

    • This refers to the small deviation in the movement of Earth’s geographical poles.
    • The normal amplitude of the Chandler wobble is about three to four metres at Earth’s surface, but from 2017 to 2020 it disappeared.

    (5) Other propositions

    • Activities that push mass towards the centre of the Earth will hasten the planet’s rotation.
    • Anything that pushes mass outwards will slow down the spin, a report noted.

    What can happen if the Earth continues to spin faster on a sustained basis?

    • To ensure that the time on clocks matches the speed of the Earth’s rotation, a system of leap seconds has been used since the 1970s.
    • They involve one-second adjustments to Universal Coordinated Time (UTC), the time standard used to synchronize clocks around the world.
    • Due to the long-term slowing in the planet’s spin, 27 leap seconds have been added to UTC.
    • However, if the Earth continues to spin faster and days subsequently become shorter, scientists may have to introduce the first ever ‘negative leap second,’ which involves subtraction of a second from clocks.

     

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  • Cabinet nod for Glasgow Climate Pledges

    India ratified pledges made by Prime Minister in Glasgow to accelerate the country’s reliance on renewable energy to power the economy and be effectively free from use of fossil fuels by 2070.

    Why discuss them?

    • The approved pledges were fewer than those PM committed to.

    What is NDC (Nationally Determined Commitments)?

    • NDCs are at the heart of the Paris Agreement and the achievement of these long-term goals.
    • They embody efforts by each country to reduce national emissions and adapt to the impacts of climate change.
    • The Paris Agreement (Article 4, paragraph 2) requires each Party to prepare, communicate and maintain successive NDCs that it intends to achieve.
    • Parties shall pursue domestic mitigation measures, with the aim of achieving the objectives of such contributions.
    • The agreement requests each country to outline and communicate their post-2020 climate actions, known as their NDCs.

    India’s NDC

    • India’s NDC, or nationally determined commitments, have been updated with these two promises, both of which are enhancements of existing targets, and would be submitted to the UN climate body.
    • The 2015 Paris Agreement requires every country to set self-determined climate targets which have to be progressively updated with more ambitious goals every few years.
    • India’s first NDC was submitted in 2015, just before the Paris Agreement was finalised.

    India’s original NDC contained three main targets for 2030:

    1. A 33 to 35 per cent reduction in emissions intensity (or emissions per unit of GDP) from 2005 levels
    2. At least 40 per cent of total electricity generation to come from non-fossil renewable sources
    3. An increase in forest cover to create an additional carbon sink of 2.5 to 3 billion tonnes of carbon dioxide equivalent

    Commitment made at Glasgow

    • At the Glasgow meeting last year, Modi promised to strengthen India’s climate commitments.
    • He made five promises, and called it the ‘Panchamrit’, the nectar that Indians prepare using five ingredients.
    • Two of these were upward revision of existing targets, the ones that have been made official and put in the updated NDC. Accordingly,
    1. India will now reduce its emission intensity by at least 45 per cent, instead of just 33 to 35 per cent, from 2005 levels by 2030.
    2. Also, it would now ensure that at least 50 per cent of its total electricity generation, not just 40 per cent, would come from renewable sources by 2030.
    3. The forestry target has not been touched.

    India’s climate targets: Existing and New

    • PM had said that at least 500 GW of India’s installed electricity generation capacity in 2030 would be based on non-fossil fuel sources.
    • Also, he had promised that the country would ensure avoided emissions of at least one billion tonnes of carbon dioxide equivalent between now and 2030.
    • These two promises have not been converted into official targets.
    • But these are closely linked with others, and any progress on official targets would get reflected in these goals as well.

    What about Net Zero?

    • Modi had also announced a net zero target for India for the year 2070.
    • Net zero is a situation in which a country’s greenhouse gas emissions are offset entirely, either by absorption of carbon dioxide.
    • This may be done through natural processes like photosynthesis in plants, or through physical removal of greenhouse gases using futuristic technologies.
    • But net zero is a long-term target and does not qualify to be included in the NDC which seeks five to 10 year climate targets from countries.

    India’s progress

    • The upward revision of the two climate targets — those relating to reductions in emissions intensity and proportion of non-fossil sources in electricity generation — do not come as a surprise.
    • India is on way to achieve its existing targets well ahead of the 2030 timeline.
    • India’s emissions intensity was 24 per cent lower than the 2005 levels in the year 2016 itself, the last year for which official numbers are available.
    • It is very likely that the 33 to 35 per cent reduction target has already been achieved, or is very close to being achieved.
    • A further reduction of 10-12 per cent from here, to meet the new target, does not appear too challenging, even though these reductions get progressively tougher to achieve.
    • The other target — having at least 40 per cent of electricity coming from non-fossil fuels — has officially been reached.

    Tricky Glasgow promises

    Two promises that Modi had made in Glasgow have not been converted into official targets:

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  • UN declares Access to Clean, Healthy Environment as Universal Human Right

    Every person on the planet has the right to live in a clean, healthy environment, as declared United Nations (UN) in a historic resolution.

    Access to Clean, Healthy Environment

    • The resolution recognizes the right to a clean, healthy and sustainable environment as a human right essential for the full enjoyment of all human rights and, among others.
    • It calls upon States and international organizations to adopt policies and scale up efforts to ensure a clean, healthy and sustainable environment for all.
    • The landmark development demonstrates that the member states can unite in the collective fight against the triple planetary crisis of climate change, biodiversity loss and pollution.
    • The declaration sheds light on almost all the rights connected to the health of our environment.
    • The declaration adopted by over 160 UN member nations, including India, is not legally binding.

    Why such move?

    • This right was not included in the Universal Declaration of Human Rights, 1948.
    • So, this is a historic resolution that will change the very nature of international human rights law.
    • The resolution will help to reduce environmental injustices and protection gaps.
    • It can empower people, especially those in vulnerable situations, including environmental human rights defenders, children, youth, women and indigenous people.

    Landmark resolution after 50 years

    • Some 50 years ago, the United Nations Conference on the Environment in Stockholm concluded with a resolution placing environmental issues at the global forefront.
    • Today, over 176 countries have adopted environmental framework laws on the basis of it.
    • From a foothold in the 1972 Stockholm Declaration, these rights have been integrated into constitutions, national laws and regional agreements.
    • In October 2021, it was recognised by the UN Human Rights Council.

    What were other such developments?

    • July 28, 2010, the UN general assembly recognised the right to water and sanitation through its resolution.
    • It stated that clean drinking water and sanitation “are essential to the realisation of all human rights”.
    • In response to this, governments across the world have changed their laws and regulations related to water and sanitation.

    Issues over this declaration

    • The words’ ‘clean’, ‘healthy’ and ‘sustainable’ lack an internationally agreed definition.
    • The text fails to refer to the foundational principle of equity in international environmental law.
    • Nevertheless, this has given more power in the hands of environmental activists to question environmentally destructive actions and policies.

    Back2Basics: Right to Clean Environment in India

    • The right to life has been used in a diversified manner in India.
    • It includes, inter alia, the right to survive as a species, quality of life, the right to live with dignity and the right to livelihood.
    • In India, this has been expressly recognised as a constitutional right under Article 21.
    • It states: ‘No person shall be deprived of his life or personal liberty except according to procedures established by law.’
    • The Supreme Court expanded this negative right in two ways.
    1. Firstly, any law affecting personal liberty should be reasonable, fair and just.
    2. Secondly, the Court recognized several unarticulated liberties that were implied by article 21.
    • It is by this second method that the Supreme Court interpreted the right to life and personal liberty to include the right to a clean environment.

     

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  • Heat Waves across the Europe

    The UK posted its highest temperature ever recorded — crossing 40°C.  Parts of France, Spain and Portugal recorded temperatures between 42 and 46 degrees.

    Why in news?

    • Dozens of towns and regions across Europe reeled under what has been described as a “heat apocalypse”, which has caused widespread devastation this year.
    • Wildfires caused by a combination of extreme heat and dry weather have destroyed 19,000 hectares of forest in southwestern France.

    What is a Heatwave and when is it declared?

    • Heatwaves occur over India between March and June.
    • IMD declares a heatwave event when the maximum (day) temperature for a location in the plains crosses 40 degrees Celsius.
    • Over the hills, the threshold temperature is 30 degrees Celsius.

    How are they formed?

    • Heatwaves form when high pressure aloft (3,000–7,600 metres) strengthens and remains over a region for several days up to several weeks.
    • This is common in summer (in both Northern and Southern Hemispheres) as the jet stream ‘follows the sun’.
    • On the equator side of the jet stream, in the upper layers of the atmosphere, is the high pressure area.
    • Summertime weather patterns are generally slower to change than in winter. As a result, this upper level high pressure also moves slowly.
    • Under high pressure, the air subsides (sinks) toward the surface, warming and drying adiabatically, inhibiting convection and preventing the formation of clouds.
    • Reduction of clouds increases shortwave radiation reaching the surface.
    • A low pressure at the surface leads to surface wind from lower latitudes that brings warm air, enhancing the warming.
    • Alternatively, the surface winds could blow from the hot continental interior towards the coastal zone, leading to heat waves.

    Following criteria are used to declare a heatwave:

    To declare heatwave, the below criteria should be met at least in 2 stations in a Meteorological subdivision for at least two consecutive days and it will be declared on the second day.

    a) Based on Departure from Normal

    • Heat Wave: Departure from normal is 4.5°C to 6.4°C
    • Severe Heat Wave: Departure from normal is >6.4°C

    b) Based on Actual Maximum Temperature (for plains only)

    • Heat Wave: When actual maximum temperature ≥ 45°C
    • Severe Heat Wave: When actual maximum temperature ≥47°C

    How long can a heatwave spell last?

    • A heatwave spell generally lasts for a minimum of four days.
    • On some occasions, it can extend up to seven or ten days.

    Impact of Heat Waves

    • Heat Strokes: The very high temperatures or humid conditions pose an elevated risk of heat stroke or heat exhaustion.
    • Healthcare crisis: Effects from extreme heat are also associated with increased hospitalisations and emergency room visits, increased deaths from cardio-respiratory and other diseases, mental health issues, adverse pregnancy and birth outcomes, etc.
    • Productivity loss: Extreme heat also lessens worker productivity, especially among the more than 1 billion workers who are exposed to high heat on a regular basis.
    • Risk of Wildfires: The heat domes act as fuel to wildfires, which destroys a lot of land area every year in countries like the US.
    • Prevents Cloud Formation: The condition also prevents clouds from forming, allowing for more radiation from the sun to hit the ground.
    • Effect on Vegetation: The trapping of heat can also damage crops, dry out vegetation and result in
    • Increased Energy Demands: The sweltering heat wave also leads to rise in energy demand, especially electricity, leading to pushing up rates.
    • Power Related Issues: Heat waves are often high mortality disasters.
    • Infrastructure failure: Avoiding heat-related disasters depends on the resilience of the electrical grid, which can fail if electricity demand due to air conditioning use exceeds supply.

    What is behind the extreme heat waves in Europe?

    Ans. Climate change, but exactly how

    • Scientists are near-unanimous that the heat waves are a result of climate change caused by human activity.
    • Global temperatures have already risen by more than 1°C , and studies in the UK had shown that a one degree rise in temperature raises the probability of the country witnessing 40°C by ten times.
    • The rising global temperature, which this year led to deviations above the normal by as much as 15 degrees in Antarctica, and by more than 3 degrees in the north pole.

    Major factor: Changes in old wind patterns

    • In the case of the US, the record temperatures are being linked to changes in the jet stream — a narrow band of westerly air currents that circulate several km above the earth’s surface.
    • While a conventionally strong jet stream would bring cooler air from the northern Atlantic, in recent years the jet stream has weakened and split into two.
    • This has led to intense and more frequent heat waves over parts of the American continent.

     

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  • Does Tropical Ozone Hole exist?

    A new ozone hole has been detected over the tropics, at latitudes of 30 degrees South to 30 degrees North, a recent study claimed. But some experts are divided over this.

    Do you know?

    The Antarctic ozone hole — one of the deepest, largest gap in the ozone layer in the last 40 years — has closed, according to the World Meteorological Organization (WMO).

    What is Ozone and Ozone Layer?

    • An ozone molecule consists of three oxygen atoms instead of the usual two (the oxygen we breathe, O2, makes up 21% of the atmosphere).
    • It only exists in the atmosphere in trace quantities (less than 0.001%), but its effects are very important.
    • Ozone molecules are created by the interaction of ultra-violet (UV) radiation from the Sun with O2 molecules.
    • Because UV radiation is more intense at higher altitudes where the air is thinner, it is in the stratosphere where most of the ozone is produced, giving rise to what is called the ‘ozone layer’.
    • The ozone layer, containing over 90% of all atmospheric ozone, extends between about 10 and 40km altitude, peaking at about 25km in Stratosphere.

    Why need Ozone Layer?

    • The ozone layer is very important for life on Earth because it has the property of absorbing the most damaging form of UV radiation, UV-B radiation which has a wavelength of between 280 and 315 nanometres.
    • As UV radiation is absorbed by ozone in the stratosphere, it heats up the surrounding air to produce the stratospheric temperature inversion.

    What is Ozone Hole?

    • Each year for the past few decades during the Southern Hemisphere spring, chemical reactions involving chlorine and bromine cause ozone in the southern polar region to be destroyed rapidly and severely.
    • The Dobson Unit (DU) is the unit of measure for total ozone.
    • The chemicals involved ozone depletion are chlorofluorocarbons (CFCs for short), halons, and carbon tetrachloride.
    • They are used for a wide range of applications, including refrigeration, air conditioning, foam packaging, and making aerosol spray cans.
    • The ozone-depleted region is known as the “ozone hole”.

    Tropical Ozone Hole

    • According to the study, the ozone hole is located at altitudes of 10-25 km over the tropics.
    • This hole is about seven times larger than Antarctica, the study suggested.
    • It also appears across all seasons, unlike that of Antarctica, which is visible only in the spring.
    • The hole has become significant since the 1980s. But it was not discovered until this study.

    What caused an ozone hole in the tropics?

    • Studies suggested another mechanism of ozone depletion: Cosmic rays.
    • Chlorofluorocarbon’s (CFC) role in depleting the ozone layer is well-documented.
    • The tropical stratosphere recorded a low temperature of 190-200 Kelvin (K).
    • This can explain why the tropical ozone hole is constantly formed over the seasons.

    Significance of the finding

    • The tropical ozone hole, which makes up 50 percent of Earth’s surface, could cause a global concern due to the risks associated with it.
    • It is likely to cause skin cancer, cataracts and other negative effects on the health and ecosystems in tropical regions.

    Back2Basics: Antarctic Ozone Hole

    • The Antarctic “ozone hole” was discovered by British Antarctic Survey scientists Farman, Gardiner and Shanklin in 1985.
    • It was caused by the chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive.
    • Though localized and seasonal, an increase in the amount of chlorine present in active, ozone-destroying forms.

    Role of PSCs

    • The polar stratospheric clouds in Antarctica are only formed when there are very low temperatures, as low as −80 °C, and early spring conditions.
    • In such conditions, the ice crystals of the cloud provide a suitable surface for the conversion of unreactive chlorine compounds into reactive chlorine compounds, which can deplete ozone easily.

     

    Try this PYQ

    Q.Consider the following statements:

    Chlorofluorocarbons, known as ozone-depleting substances are used:

    1. In the production of plastic foams
    2. In the production of tubeless tyres
    3. In cleaning certain electronic components
    4. As pressurizing agents in aerosol cans

    Which of the statements given above is/are correct?

    (a) 1, 2 and 3 only

    (b) 4 only

    (c) 1, 3 and 4 only

    (d) 1, 2, 3 and 4

     

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  • What are Cloudbursts?

    At least eight people have died after a cloudburst occurred at the Amarnath Cave Shrine near Pahalgam in south Kashmir.

    What is a Cloudburst?

    • Cloudbursts are short-duration, intense rainfall events over a small area.
    • According to the IMD, it is a weather phenomenon with unexpected precipitation exceeding 100mm/h over a geographical region of approximately 20-30 square km.

    What causes Cloudburst?

    • A study published last year studied the meteorological factors behind the cloudburst over the Kedarnath region.
    • They analysed atmospheric pressure, temperature, rainfall, cloud water content, cloud fraction, cloud particle radius, cloud mixing ratio, total cloud cover, wind speed, wind direction, and relative humidity during the cloudburst, before as well as after the cloudburst.
    • The results showed that during the cloudburst, the relative humidity and cloud cover was at the maximum level with low temperature and slow winds.
    • It is expected that because of this situation a high amount of clouds may get condensed at a very rapid rate and result in a cloudburst.

    Impact of climate change

    • Several studies have shown that climate change will increase the frequency and intensity of cloudbursts in many cities across the globe.
    • As temperatures increase the atmosphere can hold more and more moisture and this moisture comes down as a short very intense rainfall for a short duration.
    • This results in flash floods in the mountainous areas and urban floods in the cities.
    • Also, there is evidence suggesting that globally short-duration rainfall extremes are going to become more intense and frequent.

    Try this PYQ

    Q.During a thunderstorm, the thunder in the skies is produced by the:

    1. meeting of cumulonimbus clouds in the sky
    2. lightning that separates the nimbus clouds
    3. violent upward movement of air and water particles

    Select the correct option using the codes given below:

    (a) 1 only

    (b) 2 and 3 only

    (c) 1 and 3 only

    (d) None of the above

     

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