Seven things every journalist should know about climate change08 December 2013 |
How do we know what we know about the climate?
Scientists use weather stations, balloons, satellites and other instruments that measure the properties of our climate and atmosphere to create a picture of the current situation. This includes measuring temperature on land and the surface of the sea, the concentration of carbon dioxide in the atmosphere, the intensity of storms, the density of forests and the sources of greenhouse gas emissions. To get a picture of our past climate they need to use different methods. One way is to study the rings that form in tree trunks with each year’s growth. Their size and other properties reveal something – but not everything – about the local climate in the year that each ring grew. Another approach is to drill out long cores of ice and examine the contents of the small air bubbles within the ice. The bubbles contain a sample of the air and scientists can use its properties to estimate the temperature, precipitation, concentration of greenhouse gases and amount of forest fires at the time the ice formed. They have analysed gas trapped in ice cores to understand how our climate has changed over hundreds of thousands of years. To get a picture of our future climate, scientists use computer models that draw upon thousands of pieces of information about the current and past climates to make predictions about what will happen if greenhouse gas emissions continue to rise. Details about Africa's main climatic patterns and how they might change can be found here.
Climate or weather? Change or variability?
Weather is what we experience from day to day. Climate refers to the average conditions a place experiences over many years. Climate variability refers to natural changes through which the conditions differ from the long-term average. This can include periodic changes in rainfall linked to monsoons or to the natural events called “El Niño” and “La Niña” through which ocean currents affect rainfall. Climate change, by contrast, refers to long-term (decades or longer) trends such as the increase in the global average temperature over the past century. It also includes long term changes in climate variability such as changes to the number and scale of droughts, floods and other extreme events. When scientists and policymakers talk about “climate change” today they tend to mean the portion of climate change that human activities cause.
How do human activities affect the climate?
Some gases such as carbon dioxide can trap heat in the Earth’s atmosphere, through a phenomenon scientists call the greenhouse effect. Many human activities emit these greenhouse gases. When we burn fossil fuels such as coal and oil to produce electricity or drive cars, or when we clear forests to grow crops more of these emissions reach the atmosphere. Ever since the start of the Industrial Revolution in the mid-18th century, these gases have increased in concentration. At the same time the Earth has experienced a gradual warming. This global warming is the cause of the climate change that scientists say we need to understand and limit.
Impacts of Climate Change
The immediate impacts of rising temperatures include rising sea levels, less predictable weather and more extreme events such as droughts, floods and storms. The changing temperature and rainfall patterns can produce additional effects on water supplies, on crops and their pests and pollinators, and on organisms that cause disease. They can also have physical impacts on infrastructure, and all of these impacts can combine to create additional social, economic and political impacts. While it is difficult to prove that any single event is the result of climate change, many climatic trends and events that have been observed already are consistent with scientific predictions.
Mitigation and adaptation
The two main strategies for reducing the threat climate change poses are mitigation and adaptation. Mitigation refers to any activities that reduce the overall concentration of greenhouse gases in the atmosphere. This includes efforts to switch from fossil fuels to renewable energy sources such as wind and solar, or to improve energy efficiency. In also includes efforts to plant trees and protect forests, or to farm land in ways that prevent greenhouse gases from entering
the atmosphere. Adaptation refers to activities that make people, ecosystems and infrastructure less vulnerable to the impacts of climate change. This includes things like building defences to protect coastal areas from rising seas, switching to drought or flood resistant crop varieties, and improving systems to warn of heat-waves, disease outbreaks, droughts and floods.
The Intergovernmental Panel on Climate Change
The main scientific authority on climate change is the Intergovernmental Panel on Climate Change (IPCC), which the UN set up in 1988. The IPCC gathers thousands of scientists to review the global body of knowledge about climate change and summarise it in reports that policymakers can use. Every few years the IPCC produces an Assessment Report. Before the IPCC published these, scientists first review them and then governments review and endorse them. The 4th Assessment Report (2007) said that there was no doubt now that the atmosphere was warming, that human activities were 90 per cent likely to be the cause of most of the recent warming and that the impacts of climate change could be sudden and irreversible.
The UN Framework Convention on Climate Change
The UN Framework Convention on Climate Change (UNFCCC) is an international treaty that nearly 200 governments agreed in 1992 with the aim of preventing dangerous climate change. This treaty produced the Kyoto Protocol, the agreement that required some industrialised countries to reduce their emissions of greenhouse gases. Each year the countries that are party to the UNFCCC meet to review progress and negotiate new action.