Explainer: What you need to know about greenhouse effect and its threat to humanity?

Ahram Online , Monday 19 Sep 2022

Climate change is widely considered as an existential issue for humanity as serious climate impacts are already affecting every continent.

File photo: plumes of smoke rise from Europe s largest lignite power plant in Belchatow, central Poland. (AP)


For over a century now, scientists have known that human-caused greenhouse gases are warming the planet. Climate scientists began more than four decades ago to seriously sound the alarm about the dangers posed by unrestricted emissions of greenhouse gases such as carbon dioxide from the burning of fossil fuels.

A new flagship UN report on climate change issued in April, which indicates that harmful carbon emissions from 2010-2019 have never been higher in human history, is proof that the world is on a “fast track” to disaster, UN Secretary-General Antonio Guterres warned. Scientists are now arguing that it is “now or never” to limit global warming to 1.5 degrees.

Reacting to the latest findings of the Intergovernmental Panel on Climate Change (IPCC), Guterres insisted that unless governments everywhere reassess their energy policies, the world will become uninhabitable.

What is the greenhouse effect? How does it warm the Earth?

The basic physics of greenhouse effect has been understood for well over a century. The sun pours out intense amounts of radiation across the electromagnetic spectrum, including ultraviolet and infrared. The sun’s peak intensity is in visible light spectrum. Of the solar energy hitting the top of the atmosphere, one third is reflected back into space – by the atmosphere itself and the Earth’s surface (land, ocean, and ice).

The rest is absorbed, mostly by the Earth, especially our oceans.

This process heats up the planet. The Earth reradiates the energy it has absorbed mostly as heat in the form of infrared radiation. Some naturally occurring atmospheric gases let visible light escape through into space while trapping certain types of infrared radiation.

These greenhouse gases, including water vapour, methane (CH4), and carbon dioxide (CO2), trap some of the reradiated heat, so they act as a partial blanket that helps keep the planet as much as 15 degrees Celsius warmer than it otherwise would be, which is ideal for us humans.

At the dawn of the Industrial Revolution 250 years ago, CO2 levels in the atmosphere were approximately 280 parts per million (ppm). Since then, humankind has been pouring billions of tons of extra greenhouse gases into the atmosphere, causing more and more heat to be trapped.

The main human-caused greenhouse gas is CO2, and the rate of growth of human-caused CO2 emissions has been accelerating. Emissions have been in recent years six times higher than they were in 1950.

Why such phenomenon is a threat to humanity?

Scientists view warming as a settled fact because so much evidence points to that conclusion. For instance, the 1980s were the warmest decade on record at the Earth’s surface. That record was then topped by the 1990s. And again, the 2000s were the hottest year on record. The year 1998 was the hottest on record until 2005, and then 2010 topped 2005, and then 2014 became the hottest year on record at the time.

In the meantime, the United Nations said in a new report issued in September 2022 that the world is still “heading in the wrong direction.”

“This year’s United in Science report shows climate impacts heading into uncharted territories of destruction,” UN Secretary-General said in mid-September in a video message commenting on the report’s findings.

Guterres said “this year’s report shows that we are still way off track,” citing the floods in Pakistan, heat waves in Europe, droughts in places such as China, the Horn of Africa, and the United States – and pointed the finger at fossil fuels.

The report indicates that climate-related disasters kill 115 people and cost $200 million a day on average – five times greater than 50 years ago.

The United in Science report cited a 48 percent chance that global temperature rise compared to pre-industrial times will reach 1.5 degree Celsius (2.7 Fahrenheit) in the next five years, adding that a 93 percent chance that one year in the next five will see record heat.

Guterres said G20 countries are responsible for 80 percent of emissions. All countries – with the G20 leading the way – must boost their national emissions reduction [targets] and must limit the world’s temperature rise to 1.5 degrees, the UN Secretary-General said.

“It is a scandal that developed countries have failed to take adaptation seriously, and shrugged off their commitments to help the developing world,” he said.

The International Energy Agency (IEA) has recently stated that 48 African countries have requested over $1.2 trillion of international financial support by 2030 to implement their Nationally Determined Contributions (NDCs). However, only a fraction of that money has been made available so far, with wealthy states failing to meet their $100 billion-a-year pledge to developing nations.

With many are questioning the credibility of those commitments, the climate-related financial pledge for poor nations that suffer as a result of emissions – mainly produced by rich G20 countries – will play a major role at the 27th UN Climate Change Conference that will be hosted in Egypt, on behalf of Africa, in November.


- Joseph Romm’s book ‘Climate Change: What Everyone Needs to Know’, published by Oxford University Press

- United Nations statements and reports

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