Decades' Hiatus on Climate Change: Why?

Story by: Sean Kook

Visuals by: Noah Weinberg

Date: 8/15/21

Despite recent efforts to revolutionize sources of energy from carbon-fueled gas tanks and fossil fuels to solar and hydro-powered plants, carbon emissions have been dramatically increasing in the past decades. For instance, the United States Environmental Protection Agency revealed that net emissions of greenhouse gases from human activities grew by 43% from 1990 to 2015. Moreover, emissions of carbon dioxide, which is responsible for about ¾ of total emissions, increased by 51% over this period. With the immense accretion of carbon footprints caused by human activities such as transportation and cooking, accompanied by increased human population, one might reasonably expect a harrowing rate of global warming. However, scientific data gathered in the recent two decades do not satisfy this expectation, a confusion which avid environmentalists find challenging to explain to their less aware friends. In particular, there has been a mysterious hiatus on accelerating climate change since 1998. On the eve of the 21st century, the warming rate on Earth was predicted to be 0.21Cº per decade, but new study has revealed that the global temperature has in fact been rising at 0.04Cº per decade, according to a UK Met Office in Exeter and the Climatic Research Unit at the University of East Anglia in Norwich.

One theory suggested by a group of data scientists in London proposes that small volcanoes and certain Chinese industries could have pumped extra aerosols into the atmosphere, which reflect sunlight back into space. The function of stratospheric aerosol particles was tested with a satellite in which a group of scientists measured the specific nanometers of ultraviolet light entering and leaving the stratosphere. Numerous studies revealed, however, that this natural protection of sunlight accounted for just 20% of the hiatus at best, reasoning that these aerosols were only specific to certain regions and could not have compensated for lowering the level of carbon emissions.

Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, published a more promising theory, explaining that the El Niño effect during 1997-1998 pumped enormous amount of heat out of the oceans and into the atmosphere, which may been a factor in the overestimation of the planetary warming rate. The aftermath of this process, Trenberth explains, may have put the entire equatorial Pacific oceans into a “sustained cold state” which may have decelerated the warming rate by a large amount. This sustained period of cooling is what is known as El Niña, the negative effect of the Pacific Decadal Oscillation (PDO). Surprisingly this phenomenon was established in just 1997 which observes the variation in global temperature that occurs every 15-30 years. In its positive phase (El Niño), the upwelling of warm water in oceans results in warmer temperatures and in its negative phase (el Niña), the warm water gets pushed down into the deep oceans and the cool water at the surface lowers global temperatures. A 2000 study showed an increase of heat entering the deep oceans after 1998, meaning cool water was evaporating into the atmosphere, preventing the warming from increasing more rapidly.

What we must take away from this hiatus is not a sigh of relief nor should we place comfort in hopes for the planet’s natural balancing of global temperature, but a greater sense of alarm that even at the Earth’s temporary cooling stage, temperature is steadily increasing. In fact, scientists predict that the piling of warm water in the western Pacific will soon reach its limit; and when it gets so high, the missing heat will reappear from upwelling and, combined with the decade’s worth of greenhouse gas emissions, temperatures might spike again in degrees unprecedented before. It is imperative, therefore, that people be more conscious of their carbon uptake as greenhouse gas-related activity can lead to increased climate variability. Long lasting global heat waves and cold snaps are all perceivable possibilities that can only exacerbate the current environmental catastrophe. Hopes must be placed not on the planet’s remaining endurance on human activities but rather on people’s growing awareness of the climate situation and their ability to make cleaner judgement with active reflection on the warming world.


"Climate change: The case of the missing heat"
Climate Change Indicators: Greenhouse Gases | US EPA
CO2 Emissions