Why do Global Sea Surface Temperatures Matter?

General Studies Paper -3 

Context: Almost 90 per cent of the extra heat trapped by greenhouse gases has been absorbed by the oceans, making them steadily warmer over the decades, according to the Copernicus Climate Change Service (C3S).

About:

• The average global sea surface temperature (SST)for February 2024 stood at 06 degree Celsius, the highest ever in a dataset that goes back to 1979, as per the Copernicus Climate Change Service (C3S).
• The previous record of 20.98 degree Celsius was set in August 2023.

Why are the oceans getting warmer?

• Human factors:Since the Industrial Revolution kicked off in the 19th Century, human activities such as burning fossil fuels have released high levels of greenhouse gases (GHGs) in the atmosphere.
• Carbon dioxide, methane, ozone, and nitrous oxide are some of the notable GHGs, which essentially trap heat in the atmosphere and contribute to global warming.
• As a result, the average global temperature has risen at least 1.2 degree Celsius above pre-industrial times.
• Warming Rate:The top part of the ocean is warming up about 24% faster than it did a few decades ago, and that rate is likely to increase in the future.
• Absorption by oceans:Almost 90 per cent of the extra heat trapped by GHGs has been absorbed by the oceans, making them steadily warmer over the decades.
• El Niño: A weather pattern that refers to an abnormal warming of surface waters in the equatorial Pacific Ocean has contributed to both ocean warming and rising global surface temperatures.

Why are rising sea surface temperatures a cause of worry?

• Impact on Marine Life:Higher ocean temperatures can have irreversible consequences for marine ecosystems.
• For instance, warmer oceans lead to an increase in ocean stratification— the natural separation of an ocean’s water into horizontal layers by density, with warmer, lighter, less salty, and nutrient-poor water layering on top of heavier, colder, saltier, nutrient-rich water.
• The rise in temperatures made it harder for water layers to mix with each other: Due to this, oceans are able to absorb less carbon dioxide from the atmosphere and the oxygen absorbed isn’t able to mix properly with cooler ocean waters below, threatening the survival of marine life.
• Effect on nutrient circulation:Nutrients are also not able to travel up to the surface of the oceans from below. This could threaten the population of phytoplankton — single-celled plants that thrive on the ocean surface and are the base of several marine food webs.
• Phytoplankton are eaten by zooplankton, which are consumed by other marine animals such as crabs, fish, and sea stars. Therefore, if the phytoplankton population plummets, there could be a collapse of marine ecosystems.
• Marine heat waves (MHWs):Warmer oceans cause marine heat waves (MHWs), which occur when the surface temperature of a particular region of the sea rises to 3 or 4 degree Celsius above the average temperature for at least five days.
• Between 1982 and 2016, such heat waves have doubled in frequency and have become longer and more intense, according to IPCC.
• MHWs are devastating for marine ecosystems as they contribute to coral bleaching, which reduces the reproductivity of corals and makes them more vulnerable to life-threatening diseases and also impact the migration pattern of aquatic animals.
• Extreme weather events: According to several studies, higher ocean temperatures may also result in more frequent and more intense storms like hurricanes and cyclones.
• Warmer temperatures lead to a higher rate of evaporation as well as the transfer of heat from the oceans to the air. That’s why, when storms travel across hot oceans, they gather more water vapor and heat. This results in more powerful winds, heavier rainfall, and more flooding.
• Deoxygenation and Sea-Level Rise:Ocean warming leads to deoxygenation, a reduction in the amount of oxygen dissolved in the ocean and sea-level rise resulting from the thermal expansion of seawater and continental ice melting.

Suggestions/Recommendations

• Adhere to Paris agreement goals:Limiting global warming to 1.5 degrees Celsius would reduce the increase in exposure of agricultural land to drought by between 21% , 80% of the increased human exposure to heat stress can be avoided and also economic damages due to fluvial flooding can be reduced.
• Enhanced efforts: The researchers warned that more effort is needed to reduce global warming, as currently the policies in place globally are likely to result in 3 degrees Celsius of global warming.
• Expansion of protected area:The findings also showed that an expansion of protected area networks is necessary in order to deliver climate resilient biodiversity conservation.
• Mitigation as well as adaptation: Greater emphasis needs to be placed on both climate change mitigation and climate change adaptation to avoid large increases in risk to both human and natural systems.
• Restore ecosystems:A good way to combat the effects of climate change on natural systems and soak up carbon from the atmosphere is to restore ecosystems to their natural state. This has the additional benefit of restoring the natural capital bank in these areas.

Way Ahead

• These disastrous consequences of global warming are set to become worse as the world continues to get warmer.
• The World Meteorological Organisation (WMO) in its 2023 State of Global Climate report said there was a 66 percent chance that at least one of the years between 2023 and 2027 would cross the threshold of 1.5 degree Celsius above pre-in- dustrial levels.
• The way to avoid or blunt the aforementioned consequences is to reduce GHG emissions.