We are living in the 21st century, the century of climate change. The new year, 2020, was welcomed by pre-existing wildfire in the jungles of Australia and the Amazon, increasing ocean warming, increasing global warming, anthropogenic impacts of climate change, and depleting biodiversity. Such events are happening due to global warming, which, in turn, is the result of our past discoveries of ‘steam power’ and ‘fossil fuels’ at the advent of the ‘Industrial Revolution’. At that time, the policymakers, scientists and engineers did not judge the fate and impact of the discovery of fossil fuels.
On 9th May 2013, Earth achieved a ‘sad milestone of 400 ppm atmospheric CO2 concentration’, a greenhouse gas. This happened for the first time in human history. The cumulative emissions of CO2 are responsible for the increase in global warming and climate change.
At a climate change conference in 2000, Paul Crutzen, Nobel laureate in chemistry, was so alarmed by the human impacts on the biosphere since the industrial revolution that he proposed that the present era to renamed as ‘Anthropocene‘, marked by deforestation and GHGs emissions due to continuous combustion of fossil fuels.
Climate change is the biggest challenge to the future of lifeforms on Earth. ‘Earth Poles’ are getting warmer, which will result in the rise of seawater level. The dramatic collapse of Arctic sea ice, in recent years, is the sign of disaster to come much sooner. Due to this process, Arctic ice will open for sea-ice melting. As the Arctic sea-ice melts, the surface changes from being a bright reflective white to a darker blue or green, which allows more of the Sun rays to be absorbed; it is happening due to the positive feedback loop, which is adding to the rate of ocean warming.
The primary GHG responsible for global warming and climate change is carbon dioxide. The lifetime of carbon dioxide in the atmosphere is more than 100 years. The high concentration of these gases trap more infra-red radiation and remit back to earth’s surface, resulting in global warming. Oceans absorb more than 90 per cent of excess heat remitted by greenhouse gases and are continuously warming the seas at an increasing rate with disastrous impacts on Earth’s climate. Most of the excess energy stored in the oceans leads to thermal expansion and sea-level rise.
There are five oceans, namely, the Pacific, Atlantic, Indian, Southern, and Arctic, which carry about 97% of the world’s water. The oceans cover 70% of the global surface and have a significant influence on Earth’s weather and climate. Oceans absorb carbon dioxide from the atmosphere and store it for millions of years. The oceans absorb much of the solar energy which enters the earth and slowly releases that heat over several months or years. The oceans store more heat in the top three meters (10 feet).
The Indian Ocean, bordered by Asia, Africa and Australia, is the warmest in the world. The Indian Ocean remains warm all year round because there is no Arctic contact.
The effects of ocean warming are adverse and in the form of extreme weather, stronger oceanic waves, hurricanes, typhoons, tropical storms, sea ice melting, rising sea levels, coral bleaching, oxygen reduction, habitat loss, shifting of habitats, migration of marine species and damage to marine life and ecosystem.
The recent study, published in the journal Advances in Atmospheric Sciences, said that last year the ocean was 0.075 °C (0.135 °F) hotter than the historical average between 1981–2010. The world’s oceans have absorbed 228 Zetta Joules (228 billion trillion Joules) of energy in recent decades. If this level of energy is compared with the energy liberated after Hiroshima atom bomb explosion, then the amount of energy will be equivalent to four Hiroshima bombs explosion entering the oceans every second for the past 25 years.
One Hiroshima category atom bomb explosion liberates about 63,000,000,000,000 Joules of energy. So, the amount of heat we have put in the world’s oceans in the past 25 years equals 3.6 billion Hiroshima atom bomb explosions. According to this study, oceans had absorbed 25 Zetta Joules of additional energy in 2019 compared with 2018’s data of absorbed energy, and that is equivalent to about five Hiroshima bombs of heat every second, i.e., 432,000 atom bombs per day.
The study said that there was a clear link between climate-related disasters such as bushfires in southeastern Australia and warming oceans. Warmer seas mean more ‘evaporation’, more ‘rainfall’ and more ‘evaporative demand’ by the atmosphere. This, in turn, leads to ‘drying of the continents’, a major factor behind the recent wildfires of Amazon, Arctic, California and Australia. Hotter oceans also expand, leading to sea level rises.
Marine life is dying because they can’t adapt to rising temperature quickly. Localised ocean heatwave blobs have become more common over the last century and are a big threat to marine life. The frequency of blobs is expected to increase further as the planet will warm. Recently, scientists have reported that heatwave blob in the northeast Pacific Ocean was responsible for the biggest Seabird die-off on record, between 2013–2016; it was largely responsible for the death of almost a million common murres (Uria aalge), amongst other wildlife.
The United Nations Intergovernmental Panel on Climate Change in a landmark oceans report 2019 warned that tens of millions of people could be displaced from coastal areas by the end of the century.
With just 1°C of global warming since the pre-industrial period, Earth has experienced a cascade of droughts, superstorms, floods and wildfires made more likely by climate change. So, the 2015 Paris Accord aims to limit global temperature rises to “well below” 2°C, and to 1.5°C if at all possible. The 2018 IPCC report warned that the rise in global temperatures should be limited to 1.5°C to avoid dangerous impacts. This report said that global emissions must be reduced by 45% by 2030, and net-zero by 2050 to have a 50% chance of limiting temperature rises to 1.5°C in the 21st century. Since the industrial revolution in the 1750s, CO2 levels have risen more than 30% and higher than at any time in at least 800,000 years in the atmosphere.
Warming oceans are threatening food security, increasing the dispersion of diseases in marine animals, transmission of diseases from marine to humans through food, causing more extreme weather events and the loss of coastal protection. Marine life is dying because they can’t adapt quickly to rising ocean warming. Marine fishes, seabirds and marine mammals are facing very high risks from increasing temperatures. Marine life forms are migrating in search of favourable environment, habitat, food and breeding grounds. Economic losses due to ocean warming are likely to run from tens to hundreds of billions of dollars.
Coral reefs are facing coral bleaching, which increases their mortality risk. The global ocean warming has caused marine heatwaves in the Tasman Sea and other regions. Staghorn corals are one species walloped by marine heatwaves in recent years. Healthy coral reefs are a sign of good health of an ocean, which are critical habitats for young fish and other sea life.
Rising ocean temperature will also affect the vegetation and reef-building species such as corals and mangroves, which protect coastlines from erosion and sea-level rise, especially in low-lying island countries in the Pacific Ocean. Sea level rise will destroy housing and infrastructure and will force people to relocate.
Every moment, we are delaying in taking action to slow or reverse the warming, the situation will only get worse. All nations will see their economies shrink because of climate change by 2100. The Hurricane Harvey in the Gulf of Mexico in 2017 brought a massive storm that killed 82 people and resulted in a loss of $108 billion damages. In 2018, Hurricane Florence resulted in 53 deaths and damages up to $50 billion.
Global warming can affect sea levels, coastlines, ocean acidification, ocean currents, seawater, sea surface temperatures, tides, the seafloor, weather, and trigger several changes in ocean biogeochemistry. Ocean acidification, along with anthropogenic climate change, is called the “evil twin of global warming” and “the other CO2 problem”. Ocean Acidification is partially anthropogenic in origin and caused by the uptake of carbon dioxide (CO2) from the atmosphere; it involves a shift towards pH-neutral conditions rather than a transition to acidic conditions.
An estimated 30–40% of the carbon dioxide released from human activities, dissolves into oceans, rivers and lakes. Part of the carbon dioxide reacts with the water to form carbonic acid. Some of the resulting carbonic acid molecules dissociate into a bicarbonate ion and a hydrogen ion and finally help to increase the ocean acidity (H+ ion concentration). Ocean Acidification has harmful consequences for marine organisms such as depressing metabolic rates, decrease in the immune responses and bleaching of corals and shellfish.
The additional carbonic acid that forms in the oceans ultimately results in the conversion of carbonate ions into bicarbonate ions. This net decrease in the number of carbonate ions makes it more difficult for marine calcifying organisms, such as corals and plankton to form biogenic calcium carbonate, and such marine organisms become vulnerable to dissolution.
The ongoing acidification of the oceans is a threat to the future oceanic food chains, and if uncontrolled, it will result in ecological collapse of the oceans. Since the Industrial Revolution, our seas have become about 30 per cent more acidic, a rate not observed in 300 million years. This has a wide range of consequences for marine ecosystems, as well as for the billions of people who depend on the ocean for food and survival.
According to ‘Climate Central‘, since the industrial revolution, ocean pH has dropped from 8.2 to 8.1. At current emission rates, ocean pH may drop to 7.8 by the end of the century, creating an ocean more acidic than in the past 100 million years.
1. There is an urgent need to achieve the mitigation targets set by the Paris Agreement on climate change and keep the global average temperature increase below 2°C. This will help to control the impacts of ocean warming on ocean ecosystems and their services.
2. Regulate human activities in these habitats and prevent environmental degradation. This will help in conserving and protecting marine habitats.
3. Restoring marine and coastal ecosystems.
4. Introduce policies to keep fisheries production and seafood production within sustainable limits.
5. Increase investments in scientific research to measure and monitor ocean warming and its effects.
This will provide more precise data on the impacts of ocean warming and will help make the mitigation and adaptation strategies.