The causes of climate change around the world

20.FEB.09

by the St. Vincent Grammar School Young Leaders 2009.
(Theme – Going Green: Commit to Action; Join the Campaign.)

Climate change refers to a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere, and which is in addiction to natural climate variability observed over comparable time periods.{{more}}

United Nations Framework Convention on Climate Change

Quick facts: A natural blanket of greenhouse gases in the atmosphere keeps the planet warm enough for life as we know it – at a comfortable 15°C today.

Human-caused emissions of greenhouse gases have made the blanket thicker, trapping heat and leading to a global warming.

Fossil fuels are the single biggest source of human-generated greenhouse gas emissions.

The Earth’s average temperature seems to have been remarkably stable for the past 10,000 years, varying by less than 1°C, allowing human civilization to thrive at what is today a comfortable 15°C. But the very success of our civilization risks disrupting the climate that has served us so well until now.

The “blanket” of greenhouse gases that occurs naturally in the troposphere – representing less than one per cent of the entire atmosphere – serves the vital function of regulating the planet’s climate. When solar energy in the form of visible light strikes the Earth, it warms the surface. Being much cooler than the sun, the Earth emits this energy back out to space in the form of infrared, or thermal, radiation. Greenhouse gases block the infrared radiation from escaping directly into space. The resulting “natural greenhouse effect” keeps the planet some 300°C warmer than it would otherwise be and which is essential to life as we know it.

The problem we now face is that since the start of the industrial revolution some 250 years ago our emissions of greenhouse gases have been making this blanket thicker at an unprecedented speed. This has caused the most dramatic change in the atmosphere’s composition for at least 650,000 years. Unless we make significant efforts to reduce our emissions of greenhouse gases, the global climate will continue to warm rapidly over the coming decades and beyond.

The Enhanced Greenhouse Effect

The reason these “artificial” emissions are such a problem is that, in the long term, the Earth must get rid of energy at the same rate at which is receives energy from the sun. Since a thicker blanket of greenhouse gases helps to reduce energy loss to space, the climate system must adjust somehow to restore balance between incoming and outgoing energy. The result is known as the “enhanced greenhouse effect”.

The climate adjusts to the thicker blanket of greenhouse gases in large part through a “global warming” of the Earth’s surface and lower atmosphere. This rise in temperature is accompanied by other changes, for example in cloud cover and wind patterns. Some of these changes may enhance the warming further (positive feedbacks), while others may counteract it (negative feedbacks). These various interactions complicate scientists’ efforts to determine precisely how the climate will change over the decades to come.

Greenhouse Gas Emissions

Fossil fuels formed by long-dead plants and animals are the single biggest source of humanity’s greenhouse gas emissions. Burning coal, oil and natural gas releases billions of tons of carbon every year that would otherwise have reminded hidden in the Earth’s crust, as well as large amounts of methane and nitrous oxide. More carbon dioxide is released when trees are cut down and not replaced.

Meanwhile, massive herds of livestock emit methane, as do rice farms and waste dumps. The use of fertilizers produces nitrous oxide. Long-lived gases such as CFCs, HFCs and PFCs, used in air conditioning and refrigeration, are manufactured by industry and eventually enter the atmosphere. Many of these greenhouse gas-emitting activities are now essential to the global economy and form a fundamental part of modern life.