Disasters - natural and man-made, Environmental, Political, Technical

Was Gulf of Mexico oil spill world’s worst man-made disaster?

The Deepwater Horizon oil spill – variously referred to as the Gulf of Mexico oil disaster, the BP oil spill, the Macondo blowout and so forth – that began on April 20, 2010 in the Gulf of Mexico on the BP-operated Macondo Prospect site had been dubbed as the world’s worst man-made environmental disaster by the frenzied American media, local, regional and national politicians and the brazenly self-interested groups. But does it stack up to the reality check?

The accident in the Macondo field (28.74 N and 88.38 W) that resulted in the fatality of 11 workers and casualty of another 17 workers and the total discharge of 4.9 million barrels (210 million US gallons) of oil was, according to tabloid press at that time, the largest environmental disaster in American history. Although BP owned the lease of the Macondo oil site, the oil rig was owned and operated by Transocean (an American company), drilling and safety assessment responsibility was vested on Halliburton (another American company) and the blowout preventer manufacturer was Cameron International.

Deepwater Horizon oil rig in the Gulf of Mexico

Notwithstanding the delegation of operational and safety responsibilities on multiplicity of companies, particularly on American companies, the US District Judge for the Eastern District of Louisiana, Carl Barbier, ruled in his judgement in September 2014 that BP was primarily responsible for the oil spill. In July 2015, BP had to agree to pay $18.7 billion in fines, the largest corporate settlement in the United States history. Altogether, as of April 2018, the cost of clean-up, compensation to private individuals, corporate charges and other penalties on BP amounted to a staggering $65 billion. Some people from as far north as Chicago came to claim compensation in Louisiana and Texas from that oil spill (off the coast of New Orleans in Gulf of Mexica)! It was a free-for-all compensation bonanza for the American deplorables! The local press in Texas (which has a very large oil industry), as well as American national press started floating the idea that this was the opportunity to swallow up the oil company BP, which was the 6th largest oil company in the world!  

Following the accident, BP initiated a massive response to protect the beaches, wetlands and estuaries from the oil spill by commissioning skimmer ships, floating booms, controlled burns of oil and using oil dispersant (nearly 1.84 million of US gallons). Although there were several failed attempts to block the well head, finally on 15th July 2019 it was capped. On 19th September 2010, the well was declared totally sealed by the regulators.

Although it took 87 days to plug the well-head, the long-term effects were far less than what local media had whipped up. Within weeks of the leak being plugged, the traces of oil on the surface of the sea and adverse effects on the coastline had disappeared. Now, about nine years after that disaster, the effects had completely gone and the said disaster is all but a distant memory!

Tranquil deep blue sea (Gulf of Mexico)

On a recent cruise in the Gulf of Mexico, I found the area spectacular, virtually a haven of tranquillity, where a number of large cruise ships, each carrying 4,000 or more holiday makers, are operating nearly every day of the week! The water is crystal clear, there is no short-term or long-term effects at all. People in that part of the world are now more occupied with job prospects and worried about global warming, tropical storms and tornedos, extreme rainfall and floods than non-existent consequences from the oil spill.

Just to put this disaster in perspective, it must be pointed out that it was not the world’s largest man-made disaster; it was not even the largest oil disaster. The largest man-made oil disaster occurred in Kuwait during the Gulf war on 10 January 1991 when Iraqi forces deliberately opened the Kuwaiti oil valves as their war strategy. A total of 330 million gallons of oil was spilled, which was one and half times more than the Gulf of Mexico spill. The third largest oil spill occurred in the Bay of Campeche in Mexico in June 1979 when the oil well exploded releasing 140 million gallons over a period of ten months.

Accidental release of nearly 32 tons of deadly toxic gas called methyl isocyanate (MIC) on December 3, 1984 from the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, India was the world’s worst industrial disaster. The MIC is far more toxic and deadly than chlorine gas used in chemical weapons. The official estimates were that more than 3,800 people (men, women and children) died within three days of the accident and over 3,900 suffered severe and permanent disabling injury. Further afield, over 500,000 people were grievously affected by respiratory problems. Although the American Union Carbide chemical company was the major shareholder in this industrial setup, the company mendaciously managed to transfer its corporate responsibility to UCIL as a standalone entity in India and only paid $470 million (equivalent to $845 million in 2018 money) as compensation. For the death toll of nearly 350 times of Gulf of Mexico oil disaster, American company paid 75 times less compensation. That makes the life of an Indian person as 2625 less valuable than that of an American! Even now, more than 35 years later, over 30,000 people are still suffering from chronic effects – heart, lungs and digestive problems – and large areas are contaminated with toxic chemicals.

World’s worst man-made disaster was, what is now known as, the Ecocide in Vietnam when more than 20 million gallons of deadly chemicals were sprayed in the jungles of Vietnam and Laos in the 1960s and 1970s by the US military to flush out the Viet Cong guerrillas and wipe out jungles and their hiding grounds. The herbicide called Agent Orange contained dioxin, a deadly carcinogen which causes not only somatic but also genetic defects like spina bifida and other mutation illness. The Vietnamese government estimated that nearly 400,000 people had died from dioxin exposure and over 500,000 children had birth defects. No compensation of any significance or any remedial action by the US government had ever been made.

Any disaster of any sort – whether man-made or natural – is unfortunate. But when man-made disasters produced by powerful nations get away with impunity, just because the nations are powerful, that smacks at the heart of humanity. One day the perpetrators of such catastrophes could face justice of the day. 

– Dr A Rahman is an author and a columnist

Advanced science, Environmental, International, Technical

Solar radiation management can help combat climate change

In the Environmental Physics course that I teach from time to time, a student once remarked that we really do not have to worry about the deleterious effects of climate change because technology would be able to solve all the problems we are facing. At that time, I thought this viewpoint is an extreme case of technological optimism. But today, as the likelihood of international consensus to stabilise atmospheric composition of greenhouse gases seems remote while the consequences of climate change are becoming more apparent and direr, many in the scientific community believe that the potential last-ditch effort to stave off the disastrous impacts of climate change is to appeal to technology, geoengineering in particular. Even the United Nation’s Intergovernmental Panel on Climate Change considers geoengineering as a necessary Plan B if global warming does not show any signs of slowing.

Geoengineering is deliberate, large-scale manipulation of the Earth’s environment to counteract anthropogenic climate change. It encompasses two different approaches using a variety of cutting-edge technologies to undo the effects of greenhouse gas emissions. They are removal and sequestration of carbon dioxide to lower its concentration in the atmosphere and offsetting global warming by targeting the overall amount of solar energy reaching the Earth. The removal technologies were discussed in an op-ed piece published in this newspaper on November 29, 2018.

Some of the offsetting options scientists are exploring are reflecting part of the sunlight back into space before it reaches the Earth’s surface, allowing more of the heat trapped by the Earth’s surface to escape into space, and increasing the reflectivity of roofs, Arctic ice, glaciers, pavements, croplands and deserts. Known as Solar Radiation Management (SRM), these options would slow down the rise in Earth’s temperature until carbon dioxide emissions can be reduced enough to prevent catastrophic repercussions of human-driven climate change.

The fraction of incoming sunlight that is reflected back to space could readily be changed by increasing the reflectivity of the low-level clouds. This could be achieved by spraying seawater in the air where they would evaporate to form sea salt, which would seed the clouds above the oceans making them thicker and more reflective. Several simulations have confirmed that the seeding mechanism, also known as Marine Cloud Brightening, would work with the likelihood to lower temperatures at a regional level.

Another proposed cloud-based approach involves thinning the high-altitude Cirrus clouds in the stratosphere by injecting ice nuclei into regions where the clouds are formed. These wispy clouds do not reflect much solar radiation back into space, and instead trap heat in the atmosphere by absorbing thermal radiation emitted by the Earth. While this method is not technically an example of SRM, thinning Cirrus clouds would provide more pathways for the trapped heat to escape into space, and thus, potentially cool the Earth. Currently, work in this field is limited to theoretical studies at research institutions. However, research shows that a cooling of about one degree Celsius is possible by thinning the clouds globally.

Scientists have known for a long time that volcanic eruptions could alter a planet’s climate for months on end, as millions of sunlight-reflecting minute particles (aerosols) are spread throughout the atmosphere. Indeed, the “cold and miserable” summer of 1816 in China, Europe and North America is attributed to the enormous eruption of the Indonesian volcano Tambora in 1815. Though the aerosol haze produced by the Tambora eruption reflected less than one percent of sunlight, it was enough to drop global temperatures by as much as two degrees by the summer of 1816.

The 1991 explosion of Mount Pinatubo in the Philippines cooled the Earth by about 0.5 degrees, while the average global temperatures were as much as one degree cooler for the next five years after the 1883 eruption of Krakatoa in Indonesia. Furthermore, the volcanic-induced cooling of the oceans caused by Krakatoa’s eruption was enough to offset rise in the ocean temperature and sea level for a few decades.

Inspired by these eruptions and the subsequent cooling effect of their sunlight-blocking plume of sulphate particles, scientists are suggesting injecting sulphate aerosols or hydrogen sulphide in the stratosphere. The geoengineering research programme at Harvard University is currently trying to model how clouds of such particles would behave.

One of the more practical SRM techniques that can be implemented easily is whitening surfaces like roofs, croplands and pavements to reflect more sunlight back into space. By absorbing less sunlight, they would negate some of the warming effect from greenhouse gas emissions. This is what greenhouse owners do with whitewash and blinds.

The small island of Bermuda in the North Atlantic is leading the way with white roof houses that not only reflect sunlight, but also keep the homes cooler during the hotter months. A study at the Lawrence Berkeley National Laboratory in California indicates that a 1,000 square foot of white rooftop has about the same one-time impact on global warming as reducing ten tons of carbon dioxide emissions.

Ice sheets are responsible for reflecting lots of sunlight into space. So less ice in the Arctic due to melting means less heat leaving the planet. Hence, scientists want to spread tiny glass beads around the Arctic in the hopes of making the polar ice more reflective and less prone to melting. Another idea is to cover deserts and glaciers with reflective sheets.

Perhaps the most challenging concept to control solar radiation entails deploying an array of reflecting mirrors at strategic points between the Sun and the Earth—just as we all do with sunscreens and sunblocks. Calculations by space scientists at the Lawrence Livermore National Laboratory in California indicate that a mirror roughly the size of Greenland would be able to block one to two percent of solar radiation from reaching the Earth. The idea of a sunscreen is still on the drawing board.

Finally, as we transition into a new era in which human activity is shaping the Earth more than the natural forces, technology could be seen as a way of humans reshaping the planet by limiting the adverse effects of climate change. Also, because international political efforts to curtail greenhouse gas emissions have been slow in coming, solar radiation management is a possible measure to be used if climate change trends become disruptive enough to warrant extreme and risky measures.

Quamrul Haider is a professor of physics at Fordham University, New York.

Advanced science, Bangladesh, Environmental, International, Life as it is, Political, Technical

We are hurtling towards a disastrous Climate Change (Part II)

In Part I, it was shown unambiguously that human activities from the period of industrial revolution (1720 – 1800) had been the root cause for the rise of global temperature by over 1ºC due to emission of greenhouse gases into the atmosphere. As industrial activities became more and more widespread, the greenhouse gas emission and its accumulation in atmosphere increased correspondingly and the global temperature went up even higher.

Climatologists, Geoscientists, Atmospheric Scientists and so forth had been warning the world leaders of signs of increase in global temperature over and above the natural increase right from the early 1970s. As time passed, their warning became louder and louder, but the leaders of industrialised countries deliberately ignored them or rejected their scientific evidence. United States of America is, in particular, the champion of such denial right from the beginning – presidents like Ronald Reagan, George H W Bush, George W Bush and recently Donald Trump are all rejectionists of man-made global climate change.

Despite incontrovertible scientific principle and evidence that increase in carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluorocarbon (CFC) and other gases in atmosphere traps energy i.e. heat within earth’s atmosphere and thereby increase global temperature, the deniers reject all these arguments. Their short-sightedness and the damage they are inflicting on Earth are simply inexcusable.

The consequences of global increase in temperature are given below:

When air temperature increases, land surface temperature increases more than the sea temperature, as heat capacity of water is more than that of soil. What it means is that for the same amount of heat, water temperature will increase less (due to its high heat absorbing capacity) than that of soil. Similarly, when air temperature drops, land temperature drop would be more than sea temperature. Thus, sea temperature does not move up or down as much as the adjoining land mass temperature and that is why we get the moderating effect of sea.

This land-sea temperature differential is also the cause of rain, storm, snowfall etc. In the summer, land temperature increases substantially causing air to rise to high altitude and sea air being relatively cooler and heavier but laden with moisture moves towards land and gives rain. A higher temperature difference would give higher amount of rain, higher wind velocity (storm, tornado etc). Reciprocally, in the winter there would be severe snowfall, extreme cold spell etc. So, the climate change would exacerbate the nascent conditions.   

Melting of inland glaciers around the world, which would then be followed by Antarctic and Greenland ice sheets melting would cause sea-level to rise significantly. It is not only the extra volume of water from melting ice but also the thermal expansion of water due to rise in temperature that would cause sea-levels to rise and inundate large areas of land mass. It is estimated by the Inter-governmental panel on Climate Change (IPCC) that by the end of this century, the sea-level is likely to rise by at least 6ft (or even higher), if no remedial action is taken now i.e. if life continues as ‘business-as-usual’. But if action is taken urgently now to limit temperature rise to 1.50C, the sea-level rise may be contained within 3ft to 6ft.

Figure 1. Mangrove areas of Sundarbans in Bangladesh at present

In addition to that, worsening storm surge, frequent tropical storm and concentrated rainfall will affect large coastal areas and even inlands of a country, islands and low-lying areas. Bangladesh, a low-lying country, would be badly affected by sea-level rise. The average landmass there is only about 5ft above the sea level. Figure 1 shows the mangrove areas of Sundarbans in the southern part of the country at present and Figure 2 when sea level rises by the smallest estimated margin of about 3ft.  It can be seen that large areas have been inundated by the rising sea level. It is estimated that 1.3 billion people world-wide would be affected, which may require their permanent relocation or even mass migration.

Figure 2. Mangrove areas of Sundarbans in Bangladesh anticipated to be around 2050 AD.

It may be pointed out that sea-level rise does not just cause submersion of landmass, which might have been habitable area previously, but also damages arable land. Ingress of saline water precludes cultivation of crops, vegetation etc even in surrounding areas which are not inundated. 

Thawing permafrost speed up global warming, as permafrost is basically soil that stays below freezing (00C) for at least two years. Plants capture carbon dioxide (CO2) from the atmosphere by photosynthesis process and then this carbon is released when wood (in roots) decays in the soil or carbon is compressed in the natural process to form coal. In Arctic areas, wood decay or decomposition is very slow and hence these areas are regarded as carbon sink. However, decomposition increases as temperature increases causing enhanced carbon emission. The inventory of frozen carbon in permafrost is 1.5 trillion tons, which is nearly twice the amount of carbon in the atmosphere now!

Wildfires are caused due to global warming and these then contribute to further global warming. Wildfire thus has a positive (destructive) feedback effect. Trees and vegetation absorb CO2 and convert it to oxygen (O2), thus acting as sinks. Tropical forests in Indonesia, Malaysia, Brazil and in other parts of the world play a vital role in carbon sequestration. However, wildfires effectively convert the sink of carbon straight into source of carbon! The forest fires that are razing in the Amazon rain forest now, which is regarded as the lungs of the planet Earth, are extremely damaging. These forest fires are not natural wildfires; these are deliberate man-made fires to clear forest areas for agricultural use (deforestation). Man is making the planet uninhabitable. 

The effect of all these changes is causing severe disruption to the climate. Where there were moderate rainfalls, now there are severe rainfalls causing flash flood, bursting of dams, landslides etc. In 2018, there were devastating floods in Japan, North Korea and India. In 2019, bridges in North Yorkshire, England collapsed when full month’s rain fell in just four hours.

While some parts of the world were having tremendous amount of rainfall in short spell of time, others were baking in heat waves. France’s capital Paris experienced this summer (June 2019) the highest temperature of 46ºC and India experienced 50ºC. Pakistan experienced a deadly heat wave where highest recorded temperature was 54ºC!

There were unprecedented wildfires in Greece and Australia. Wildfires in the forest area called Paradise in California are devastating and becoming a regular event. Northern Finland (in Arctic Circle) and Siberia were used to be considered so cold that wildfires were thought to be incredible, but not anymore. Last year as well as this year, wildfires in those areas devastated large land mass.

In the year 2017, hurricane Irna, a category 5 storm, was the most powerful Atlantic storm in a decade to strike the Caribbean and Southern US. In addition, hurricane Harvey in Texas and hurricane Maria in Dominican Republic wrought havoc. Monsoon floods in Bangladesh and mudslides in Sierra Leone are devastating natural disasters in 2017.

The frequency and severity of these natural disasters are breaking all previous records. A natural disaster, which only 10 or 15 years ago would have been considered once in 100 years event, is now happening once or twice a decade and if runaway conditions are allowed to continue, those events may become regular events!

Donald Trump not only denies man-made climate change but also encourages activities which cause climate change. He and his right-wing coterie of extremist Republicans in America hold and promote the view that climate change is due to natural phenomenon. There is an Institute in America, called the Heartland Institute (which Trump endorses and supports) which claims to be one of the world’s “leading free market think-tanks” and promotes “free market solutions to social, economic and environmental problems”. It disputes scientific observations and knowledge on climate change (as is usual with right-wing cliques to denigrate scientific knowledge), criticises climate mitigation activities and promotes use of fossil fuels. 

When confronted with increased severity and more frequent incidences of droughts, forest and bush fires, floods, storms, tropical cyclones, cold spells etc, these climate change deniers assert these are just natural phenomena; nothing to do with human activities. Their denial is either based on sheer ignorance or moral depravity.

Dr A Rahman is an author and a columnist


Bangladesh, Environmental, International, Life as it is, Political, Technical

We are hurtling towards a disastrous climate change (Part I)

The human race is staring at the disastrous climate change of their own making. The climate change clock is ticking remorselessly; it has gone past the 11th hour and, although not exactly on the 59th minute, but not too far from it. We pride ourselves to be civilised human beings, we claim unprecedented scientific and technical achievements; but we have failed to realise the damage we have inflicted and still are inflicting on our planet and our actions are anything but civilised. A large section of the human population under the guidance and influence of ‘civilised political leaders’ in many Western and Eastern countries is in complete denial of the climatic damage!

In order to appreciate how close are we to the tipping point of the irreversible climate change, we need to look at the factors that initiate climate change. The term ‘climate change’ embodies the totality of processes like global warming, sea levels rise, loss of polar ice caps, floods, fires, droughts and so forth. These processes do not take place for no reasons; there are deep rooted reasons for these effects.

The causes for these effects are multifarious. Causes range from emission of greenhouse gases from uncontrolled industrial activities, excessive exploitation of Earth’s resources, deforestation, rise in human population, demands for improved standards of living, increased air travel etc. All these factors contribute to climate change due to enhanced greenhouse gas emission. And the quantity that is primarily used to characterise climate change is the increase in global temperature.

The root cause of the increase in temperature is the increase in greenhouse gas concentration in Earth’s atmosphere. A sort of runaway situation has developed here. Increase in greenhouse gas leads to higher global temperature and higher global temperature leads to higher greenhouse gas. Unless decisive action is taken by human beings to arrest this situation, the human race is at peril. 

The legitimate question that arises here is that how can one assert this rise in global temperature leading to climate change is mainly due to human activities, when both natural processes and human activities do contribute to global temperature? That is a genuine question.  

The planet Earth had undergone over the millennia large climate swings. Scientists had looked into these variations in Earth’s climate over the past 650,000 years and found that there had been as many as seven ice ages during this period and in between ice ages there had been some warmer periods with increase in global temperatures. Modern human beings (Homo sapiens) had not yet evolved 650,000 years ago and so global temperatures could all be assigned to natural causes. There was no trend of temperature variation over this period.

When nearly 250,000 years ago, modern human beings emerged from the savannas in Africa, man started interacting with nature. But those primitive men had no way of exploiting the Earth; they were passive, subservient onlookers of nature.

Climatologists looked at the inter-glacial periods i.e. between two cold glacial spells and established a baseline temperature. After the baseline temperature was established, then any excess global temperature found over a period when human activity was known to have taken place can be assigned to human activities. This is an established scientific technique and it is applied to many scientific disciplines to separate out human activities from natural activities.

The planet Earth is blanketed by a layer of gases in the outer atmosphere. This atmosphere containing a variety of gases lets in solar radiation to come through, but blocks out or shields harmful ionising radiation from the outer skies. A small fraction of solar energy is reflected back from Earth’s surface to outer skies. Normally if the atmosphere is unpolluted, this reflected energy in the form of infrared radiation will escape to outer space. On the other hand, if there are pollutants such as carbon dioxide, methane etc, this radiation is held back and reflected towards Earth again. Thus, gradually excess energy is accumulated in the planet and its temperature goes up.

The types of gases that refuses to let infrared escape from Earth had been found to be carbon dioxide (CO2), methane gas (CH4), nitrous oxide (N2O), chlorofluorocarbon (CFC) and a few more. Atmospheric concentrations of carbon dioxide in ppm (parts per million) and methane gas in ppm over the period 1500 to the present time had been estimated by scientists and presented in the graphs below. The period 1720 to 1800 is the industrial revolution period when human activities kicked in large scale. Before this industrialisation period, humans were living in harmony with nature. It can be seen from both of these graphs that the industrial revolution was the spurt in increase in concentration which continued in accelerated fashion right up to the present day.

Greenhouse gas concentration from 1500 to 2000 AD
(Courtesy: http://www.theconversation.com)

Along with these two graphs, one should consider the rise in global temperature which is shown below. The similarity in the overall shape and pattern of these graphs is striking and one can draw conclusion that are correlated. It shows beyond doubt that the rise in temperature above the 1850 to 1900 (industrialisation period) baseline is due to increased concentration of global warming pollutants – CO2 and CH4. There are other significant pollutants such as chlorofluorocarbon (CFC), but it is not shown here.

The CO2 concentration in pre-industrialised period was between 200 to 270 ppm and Earth had a thermally stable period. But now this concentration has risen to about 350 ppm leading to about 1ºC rise in temperature. But, if the present trend continues, by the end of the coming decade the temperature may well go up more than 1.5ºC and that would bring in very harsh conditions for all forms of life on Earth.

Global average temperature and industrial baseline.
(Courtesy: http://www.theconversation.com)

From 1970s the scientists had been saying that human beings are damaging Earth’s atmosphere and its natural conditions and care should be taken to limit it or even reverse it. But political leaders of various persuasions, particularly Americans and vested interests dealing with fossil fuels, kept denying any global warming or any climate change etc. When confronted with increased severity and more frequent incidences of droughts, bush fires, floods, storms, tropical cyclones, cold spells etc, these climate deniers started saying that these are natural phenomena; nothing to do with human activities. Their denial is either based on ignorance or moral depravity.

Few countries holding such views are destroying the good work of large number of countries. Donald Trump, president of America, is the most famous deniers of all, mainly because America is the second largest polluter of the world and to limit polluting activities would cost America a lot. And hence denying the whole thing is the easy option. Pursuing such damaging policy, America, under Donald Trump, had withdrawn from the Paris Agreement in 2017.

The Paris Agreement of 2015 aims to limit global warming to 1.5ºC relative to a pre-industrial baseline. Its precise commitment is:

Holding the increase in the global average temperature to well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃ above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.

We all live in the same planet. If one country i.e. America, the second largest polluter, keeps damaging the planet for its own benefit, that would wipe out the sacrifices of large number of countries. America is pushing the Earth to a precipice for their selfish interests.

(The next Part (Part II) will deal with the likely consequences of the present predicament and the most likely prediction of the future scenario.)


  • Dr A Rahman is an author and a columnist
Bangladesh, Economic, Environmental, International, Life as it is, Technical

Our oceans: The ultimate sump

Plastic pollution

Today is “World Oceans Day,” a day observed worldwide to raise awareness about the crucial role the oceans play in sustaining life on Earth. It is also a day to appreciate the beauty of the oceans that “brings eternal joy to the soul.”

The oceans are among our biggest resources and also our biggest dumping grounds. Because they are so vast and deep, many of us believe that no matter how much garbage we dump into them, the effects would be negligible. Proponents of dumping even have a mantra: “The solution to pollution is dilution.” Really! In case they don’t know, garbage dumped into the oceans is continuously mixed by wind and waves and widely dispersed over huge surface areas.

There is a zone in the Pacific Ocean, called The Great Pacific Garbage Patch, which is a gyre of marine garbage twice the size of Texas. The garbage, mainly microplastics, were carried there by strong currents from other parts of the ocean. This is not the only floating garbage in our oceans. The Atlantic and Indian Oceans have their own garbage patches. Worse yet, the sheer size of the patches is making clean-up efforts an extremely difficult task.

Surely, human activities are impacting the oceans in drastic ways. Some of the anthropogenic environmental issues that are affecting the oceans are plastic pollution, oil spills, climate change and noise. One of the most dangerous threats the oceans may face in this century is radioactive pollution.

Each year, we dump nearly eight million tonnes of plastic—mostly grocery bags, water bottles, yogurt cups, drinking straws and plastic utensils—into the oceans. Recently, plastic has been discovered in the deepest part (11 kilometres) of the world’s oceans, Mariana Trench in the Pacific Ocean. Extremely elevated concentration of PCBs, an environment-damaging chemical banned in the 1970s, have also been found within the sediment of the trench.

While it takes hundreds of years for plastics to decompose fully, some of them break down much quicker into tiny, easy-to-swallow particles that can easily be ingested by marine species causing choking, starvation and other impairments.

Pollution of the oceans by oil spills has been one of the major concerns for a long time. The primary source of spill is offshore drilling. The process is inherently dangerous and thus, is prone to accidents. When accidents happen, and they do happen without warning, they cause massive damage to the environment—aquatic and shore—that persists for decades to come. Some oil spills happen when tankers transporting petroleum products have accidents.

If the layer of the oil is thick enough, it smothers creatures unable to move out from under it. Besides, swimming and diving birds become covered with oil, which mats their feathers, reducing their buoyancy and preventing flight. The insulative value of feathers is also lost and the birds quickly die of exposure in cold water.

The world’s largest oil spill was not an accident; it was the result of the Persian Gulf War in 1991. The second worst disaster was the spill by BP’s Deepwater Horizon offshore rig in the Gulf of Mexico in April 2010. Both incidents killed tens of thousands of birds, marine mammals, sea turtles and fish, among others.

Land and oceans together absorb slightly more than half of all the carbon dioxide emissions, with the oceans taking a greater share. When carbon dioxide dissolves in water, it forms carbonic acid. Various studies estimate that if we keep on pumping carbon dioxide into the atmosphere at the current rate, then by the year 2100, the water of the oceans could be nearly 150 percent more acidic than they are now. Such a large increase in acidity would upset the productivity and composition of many coastal ecosystems by affecting the key species at the base of the oceanic food webs. It would also reduce calcium carbonate, which is essential for building the shells and skeletons of creatures like mussels, clams, corals and oysters.

Because oceans absorb more than 90 percent of the heat that is added to the climate system, sea level is changing, albeit unevenly. It is changing unevenly as oceans do not warm uniformly across the planet, with the southern oceans warming at a faster rate. In addition, global reef systems are slowly migrating poleward as oceans around the world continue to warm.

The single most significant contribution to rising sea level is from the thermal expansion of water. Melting ice makes the second most important contribution, but only melting of land-based ice—glaciers, ice caps and ice sheets—is significant. Ice that is already floating in the water—iceberg—makes essentially no change in sea level when it melts, because the greater density of water offsets the volume of ice that is not submerged. Other factors that contribute to the rise in sea level include wind and ocean circulations, depth of the oceans, deposition of sediments by river flows and alteration of the hydrologic cycle by humans.

According to some studies, global sea level rose by about 18 cms during the last century. In the worst-case scenario, sea level could rise by two metres by the end of the year 2100. Arguably, rising sea level is among the potentially most catastrophic effects of human-caused climate change.

The oceans are no longer “The Silent World” of the famous oceanic explorer Jacques Cousteau. Today, they are being acoustically bleached by noise from seismic blasts used for offshore oil and gas exploration, marine traffic and military sonar.

Unlike plastic pollution, noise pollution does not have the visual impact that is needed to spark an outcry and force action. It is an invisible menace that is drowning out the sounds of many marine animals, including fish, use for navigation, communicating with each other, finding food, choosing mates and warning others of potential dangers.

Whales and dolphins are particularly vulnerable to noise pollution. The deafening seismic blasts and the ping of sonar are responsible for the loss of their hearing and habitat, and disruption in their mating and other vital behaviours. The disappearance of beaked whales in the Bahamas in recent years have been attributed to testing of US Navy sonar systems in the region.

From 1946 through 1993, nuclear countries used the oceans to dispose of radioactive wastes. The United States alone dumped more than 110,000 containers of nuclear material off its coasts. Russia dumped some 17,000 containers of radioactive wastes and several nuclear reactors, including some containing spent nuclear fuel.

It is highly likely that radioactive wastes would eventually leak out of the containers because of poor insulation, volcanic activity, tectonic plate movement and several other geological factors. Indeed, last month, UN Secretary General Antonio Guterres confirmed that a Cold War era concrete “coffin” filled with nuclear waste is leaking radioactive material into the Pacific Ocean. Since radiation from nuclear wastes remains active for hundreds of thousands of years, their dangerous effects will linger for a long time and will have lethal impact on marine life.

Furthermore, six nuclear submarines — 4 Russian and 2 American — lost as a result of accidents are lying at the bottom of the oceans. They represent serious threat of radioactive contamination of the oceans, too.

One of the biggest contaminations due to radiation was caused by a series of nuclear tests conducted by the USA on the sea, in the air and underwater at Bikini Atoll in the North Pacific between 1946 and 1958. The French nuclear tests carried out during 1966-1996 in French Polynesia are responsible for other cases of intense radioactive pollution of marine ecosystems.

Clearly, we are using the oceans as the ultimate sump, partly because their very immensity seems to preclude any long-term effect, and partly because they belong to no one. This cannot continue indefinitely because in order for us to survive, we have to protect the oceans. Lest we forget, life emerged from the oceans and the source of most of the oxygen we breathe are the oceans. They have been an endless source of inspiration to humankind.

Quamrul Haider is a Professor of Physics at Fordham University, New York.