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Why we need to care about the ocean when it comes to climate change?
By Liu Wei
A child learns about a rain gauge at a meteorological museum in Nanjing, Jiangsu Province on March 21, 2021. /CFP

A child learns about a rain gauge at a meteorological museum in Nanjing, Jiangsu Province on March 21, 2021. /CFP

Most people do not take the ocean into consideration when thinking about extreme weather events or as a major factor of climate change.

But the World Meteorological Organization (WMO) drew attention this year to the pivotal role of the ocean in driving the world's weather and climates on World Meteorological Day on Tuesday. 

Covering about 70 percent of the Earth's surface, the ocean is in fact a major contributor to the world's weather and the climate, and plays a crucial role in climate change. "90 percent of the excess energy that accumulates in the Earth system due to increasing concentrations of greenhouse gases, goes into the ocean," according to WMO's Provisional State of the Global Climate 2020 report.

The ocean is also essential to the global economy, carrying more than 90 percent of world trade and sustaining 40 percent of the global population living within 100 kilometers of the coast, said WMO.

It also acts as the Earth's thermostat and conveyor belt by absorbing and transforming a significant portion of the sun's radiation hitting the Earth's surface. Ocean currents form and circulate this heat around the planet, often for thousands of kilometers, thus shaping the Earth's weather and climate on global and local scales. 

But the sea is changing, with human activities as one of the major causes. Ocean temperatures are at records highs, acidification is worsening, and the rate of sea level rise has been speeding up as more sea ice is melting. 

In September 2020, Arctic sea ice appeared to have reached its annual minimum extent, with WMO warning that polar communities are suffering from abnormal coastal flooding and sea ice hazards as a result.

Many extreme weather such as droughts and fires are also linked to warming ocean temperatures. 

In recent years, there has been a surge in the number of wildfires and extended fire seasons globally due to prolonged droughts. For instance, catastrophic bushfires in Australia burned from July 2019 to March 2020, scorching over 46 million acres of land, affecting nearly 3 billion animals including 143 million mammals, 2.46 billion reptiles, 180 million birds and 51 million frogs.

The climbing ocean temperatures can also cause marine heatwaves, considered as "underwater bush fires," which can kill ecosystems such as coral reefs or impact fish migration. 

Furthermore, warm ocean temperatures also fueled a record-breaking Atlantic hurricane season in 2020, with 30 named tropical storms, including 13 hurricanes and six major hurricanes, with direct impacts in many countries in the Atlantic basin, Caribbean Sea and Gulf of Mexico. There were also intense tropical cyclones in the Indian and South Pacific Oceans in 2020.  

The storms caused significant consequence to coastal areas, showing the power of the ocean, while non-tropical ocean storms have also put lives, ships and cargo at sea at the risk. 

This year marks the beginning of UN's Decade of Ocean Science for Sustainable Development initiative (2021-2030), which aims to strengthen the management of the oceans and coasts, as well as ensure global ocean science advance to benefit ocean ecosystems and the wider society, and help tackle the climate change. 

WMO Secretary-General Petteri Taalas said the impact of the ocean heat and acidification "will be felt for hundreds of years because the ocean has a long memory."  To tackle climate change, the ocean must never be an outsider.

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