Resource 5: Global warming articles
Background information / subject knowledge for teacher
Global warming is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. As the Earth spins each day, the new heat swirls with it, picking up moisture over the oceans, rising here, settling there. It is changing the rhythms of climate that all living things have come to rely upon.
What will we do to slow this warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the face of the Earth as we know it – coasts, forests, farms and snow-capped mountains – hangs in the balance.
The ‘greenhouse effect’ is the warming that happens when certain gases in Earth's atmosphere trap heat. These gases let in light but, like the glass walls of a greenhouse, keep heat from escaping.
First, sunlight shines onto the Earth's surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, greenhouse gases (GHGs) trap some of this heat, and the rest escapes into space. The more GHGs are in the atmosphere, the more heat gets trapped.
Scientists have known about the greenhouse effect since 1824, and have calculated that the Earth would be much colder if it had no atmosphere. This greenhouse effect is what keeps the Earth's climate habitable. Without it, the Earth's surface would be an average of about 60 °F cooler. Humans can enhance the greenhouse effect by making carbon dioxide, a GHG.
Levels of GHGs have gone up and down over the Earth's history, but they have been fairly constant for the past few thousand years.
Global average temperatures have stayed fairly constant over that time as well, until recently. Through the burning of fossil fuels and other GHG emissions, humans are enhancing the greenhouse effect and warming Earth.
Scientists often use the term ‘climate change’ instead of global warming. This is because as the Earth's average temperature climbs, winds and ocean currents move heat around the globe in ways that can cool some areas, warm others, and change the amount of rain and snow falling. As a result, the climate changes differently in different areas.
Aren’t temperature changes natural?
The average global temperature and concentrations of carbon dioxide (one of the major GHGs) have fluctuated on a cycle of hundreds of thousands of years as the Earth's position relative to the sun has varied. As a result, ice ages have come and gone.
However, for thousands of years now, emissions of GHGs to the atmosphere have been balanced out by GHGs that are naturally absorbed. As a result, GHG concentrations and temperature have been fairly stable. This stability has allowed human civilisation to develop within a consistent climate.
Occasionally, other factors briefly influence global temperatures. Volcanic eruptions, for example, emit particles that temporarily cool the Earth’s surface. But these have no lasting effect beyond a few years.
Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over the course of decades.
Why is this a concern?
The rapid rise in GHGs is a problem because it is changing the climate faster than some living things may be able to adapt. Also, a new and more unpredictable climate poses unique challenges to all life.
Historically, Earth's climate has regularly shifted back and forth between temperatures like those we see today and temperatures cold enough that large sheets of ice covered much of North America and Europe.
The difference between average global temperatures today and during those ice ages is only about 5 °C (9 °F), and these swings happen slowly, over hundreds of thousands of years.
Now, with concentrations of GHGs rising, Earth's remaining ice sheets (such as Greenland and Antarctica) are starting to melt too. The extra water could potentially raise sea levels significantly.
The climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme. This means more intense major storms, more rain followed by longer and drier droughts (a challenge for growing crops), changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.
Scientists are already seeing some of these changes occurring more quickly than they had expected. 11 of the 12 hottest years since records became available occurred between 1995 and 2006.
Article 2looks at the impact of global warming in Africa. The African continent is a rich mosaic of ecosystems, ranging from the snow and ice fields of Kilimanjaro to tropical rainforests to the Saharan desert.
Although it has the lowest per capita fossil energy use of any major world region, Africa may be the most vulnerable continent to climate change because widespread poverty limits countries’ capabilities to adapt.
Signs of a changing climate in Africa have already emerged: spreading disease and melting glaciers in the mountains, warming temperatures in drought-prone areas, and sea-level rise and coral bleaching along the coastlines. The following show some related events:
Cairo, Egypt – Warmest August on record, 1998. Temperatures reached 41 °C (105.8 °F) on August 6, 1998.
Southern Africa – Warmest and driest decade on record, 1985–1995. Average temperature increased almost 0.56 °C (1 °F) over the past century.
Senegal – Sea-level rise. Sea-level rise is causing the loss of coastal land at Rufisque, on the south coast of Senegal.
Kenya – Mt Kenya’s largest glacier disappearing. 92% of the Lewis Glacier has melted in the past 100 years.
World ocean – Warming water. The world ocean has experienced a net warming of 0.06 °C (0.11 °F) from the sea surface to a depth of 10,000 feet (3,000 m) over the past 35–45 years. More than half of the increase in heat content has occurred in the upper 1,000 feet (300 m), which has warmed by 0.31 °C (0.56 °F). Warming is occurring in all ocean basins and at much deeper depths than previously thought.
Rwenzori Mountains, Uganda – Disappearing glaciers. Since the 1990s, glacier area has decreased by about 75%. The continent of Africa warmed by 0.5 °C (0.9 °F) during the past century, and the five warmest years in Africa have all occurred since 1988.
Kenya – Deadly malaria outbreak, summer 1997. Hundreds of people died from malaria in the Kenyan highlands where the population had previously been unexposed.
Tanzania – Malaria expands in mountains. Higher annual temperatures in the Usamabara Mountains have been linked to expanding malaria transmission.
Indian Ocean, Persian Gulf, Seychelles Islands – Coral Reef bleaching. Includes Seychelles; Kenya; Reunion; Mauritius; Somalia; Madagascar; Maldives; Indonesia; Sri Lanka; Gulf of Thailand [Siam]; Andaman Islands; Malaysia; Oman; India; Cambodia.
Kenya – Worst drought in 60 years, 2001. Over four million people were affected by a severely reduced harvest, weakened livestock and poor sanitary conditions.
Lake Chad – Disappearing lake. The surface area of the lake has decreased from 9,650 sq mi (25,000 km2) in 1963 to 521 sq mi (1,350 km2) today. Modelling studies indicate the severe reduction results from a combination of reduced rainfall and increased demand for water for agricultural irrigation and other human needs.
South Africa – Burning shores, January 2000. One of the driest Decembers on record and temperatures over 40 °C (104 °F) fuelled extensive fires along the coast in the Western Cape Province. The intensity of the fires was exacerbated by the presence of invasive vegetation species, some of which give off 300% more heat when burned compared to natural vegetation.
Adapted from: Climate Hot Map, Website