Climate Change: facts, impacts and solutions

The term climate change refers to long-term changes in the global climate, meaning temperature patterns and weather.

Change in the Earth’s climate are caused by natural shifts and, since the 1800s, accelerated by human activities such as burning fossil fuels (like coal, oil and gas) producing heat-trapping gases in the atmosphere.

Global Warming means the increase in the average temperature of air near the earth’s surface. Since the mid-20th century, global temperatures have risen by 0.7 degrees Celsius, mostly due to the greenhouse effect of certain gases we have introduced to the atmosphere.

Average global temperature is expected to increase by 2-7 degrees Celsius by the end of the century, with the exact degree determined by how much we reduce our greenhouse emissions today.

Of all our contributions, the most significant is Carbon Dioxide (C02) released by the burning of fossil fuels such as coal and oil. At the same time, the natural absorption of CO2 by plants and trees has simultaneously been reduced by land clearing and deforestation.

As a result, the ten warmest years on human record have all taken place within the 12-year period of 1998–2010.

Positive feedback loops, which amplify the damage, have led to a four-fold acceleration in the rate of change over the last 25 years.

This has various impacts on our planet and on our lives, including sea-level rises, extreme weather events and global food and water shortages. This could lead to massive numbers of environmental refugees flooding to areas that can still support human life.

Without urgent, radical solutions, runaway climate change will make it impossible to return the planet to the relatively stable and temperate climate which has prevailed since the last ice-age.

Time is running out, and the cost of inaction grows every day.

These facts have been confirmed and re-stated many times by the worlds leading bodies on climate change, notably the Intergovernmental Panel on Climate Change (the IPCC), a coalition of some 3000 experts from around the world.

Basic science

Climate change is what scientists refer to as the long-term movement in weather averages on Earth. Global warming refers to an increase in the average temperatures on Earth, which in turn changes patterns in the climate.

The cause of global warming is the increasing intensity of the greenhouse effect. The greenhouse effect is the process by which the atmosphere traps some of the Sun’s energy, warming the Earth enough to support life. When radiation from the Sun strikes the surface of the Earth, a portion of this energy is reflected back into space by the earth’s atmosphere.

Another part is dispersed within the atmosphere itself, and the largest amount penetrates the atmosphere to warm the surface of the Earth.

Much of the absorbed energy is radiated back from the Earth in longer infrared wavelengths. As it leaves the earth, it again interacts with the atmosphere.

Some of this re-radiated energy moves into space, but much is reflected back to the earth’s surface by gases in the earth’s atmosphere, known as greenhouse gases.

This result is similar to the warming effect of glass in a greenhouse, hence the term the greenhouse effect.

Greenhouse gases include water, (H2O), nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2). Increasing the concentration of these gases in the atmosphere boosts the atmosphere’s ability to trap the Sun’s energy. More and more of the Sun’s energy is retained within the atmosphere, leading to global warming and climate change.

Although there are natural sources of greenhouse gases, such as volcanoes, animal respiration and evaporation from the oceans, these natural sources have historically been balanced by natural carbon sinks, such as forests that store carbon for thousands of years. Human sources of greenhouse gases have unbalanced these natural forces. By far the largest part of observed warming over the past century has been caused by human activities.

Human, or ‘anthropogenic’ greenhouse gas emissions are primarily from fossil fuels. We also release greenhouse gases through deforestation. A rising population and positive feedbacks multiply these processes.

Over the last 150 years – primarily in the past 50 years – we have dug up fossil fuels and burnt them, releasing vast amounts of stored carbon back into the atmosphere in the form of CO2.

The most recent research suggests atmospheric CO2 levels are higher now than at any time in the last 2.1 million years. Throughout that period, average CO2 levels have been 280 ppm (parts per million). We are now at 388.92 ppm (parts per million)… and rising.

The presumed “safe” level for CO2 is below 350 ppm and we have been above that level for two decades. Data from ice cores shows that CO2 is now at its highest concentration for 800,000 years and is increasing at unprecedented rates – ten times faster than at any other time in the past 22,000 years.

As a result, the greenhouse effect is growing increasingly intense. The 10 warmest years in human records have all occurred in the last 12 years, and every year without radical social change is going to be hotter and hotter.

We need to act rapidly to implement solutions to climate change, in order to reduce its impacts on ecosystems and human populations, and avoid further increases in the rate of warming as a result of positive feedback effects.

The evidence

The evidence that informs our knowledge of global Warming and the greenhouse effect is historical, virtual and actual.

Historical data comes from palaeoclimatology, which involves the examination of ice-cores, water sediments, tree-rings and other proxy measurements to determine historical climate patterns. The human record of global temperatures, ocean temperatures, CO2 levels, and satellite data also provides evidence of historical climate events.

Virtual evidence takes the form of computer climate modeling. The best models reproduce past climates with accuracy and can then be used to predict future climates under likely future scenarios, such as further CO2 rises or population growth. The Intergovernmental Panel on Climate Change (IPCC) uses advanced virtual climate models to demonstrate causes, effects and strategies to prevent and reduce climate change.

Actual evidence means current science, as well as the evidence we accumulate in our own experience of the world. While its important to ignore the normal variability of climate, it is still possible to detect real trends. When historical, virtual and actual evidence all come together, such as the evidence for the melting of sea ice, then clearly we have a problem.

Palaeoclimatological evidence shows that, in addition to human-induced climate change, there is some natural variability in the climate, as well as in the levels of greenhouse gases in the atmosphere.

However despite natural variations in the climate, dramatic changes began occurring in unprecedented ways after the midpoint of the twentieth century. Current degrees of warming and rates of change are well outside the natural range, indicating that today’s climate change is not due to natural variability.

History of Climate Science

Early climate science was limited a few key thinkers distributed in different scientific fields and countries, which meant that discoveries were few and far between.

In 1824, pioneer French physicist Joseph Fourier published his idea that the atmosphere warmed the Earth enough for life to exist.

He speculated that human activities could change the atmosphere and raise global temperature averages. In the early 20th century, Swedish Nobel prize laureate Svante Arrhenius explained that the burning of fossil fuels by releasing carbon dioxide could contribute to temperature rises .

In the 1950s, there was a sharp increase of government funding from military agencies with Cold War concerns about the weather and the seas, which encouraged more systematic research into the climate.

Over the next few decades a few scientists used palaeoclimatology to retrieve historical temperatures. It appeared that grave climate change had happened within as little as a few centuries.

This finding was reinforced by virtual climate models of the general circulation of the atmosphere. Nevertheless, the scientists that reviewed the issue saw no need for any policy actions.

In the early 1970s, the rise of widespread environmental activism raised public concerns about the destructive effects of human activity. Yet the only scientific consensus was that we scarcely understood the climate system, and much more research was needed.

Previously, researchers had sought a single formula to understand the climate, but now they understood the climate as an intricate system responding to a great many influences. Nevertheless, despite the increasing intricacy of the models, many still incorporated arbitrary assumptions, which reduced reliability of the results.

Until recently, research remained disorganized, and funding was provided in irregular surges. In this context, the world’s governments created the Intergovernmental Panel on Climate Change (IPCC) to give them the most reliable advice, as negotiated between thousands of climate experts. By 2001 the IPCC managed to establish a consensus that, although the climate was so complex that we would never reach complete certainty, it was much more likely than not that the Earth would undergo severe global warming.

Today, the IPCC and other organisations continue to advance our knowledge of the climate through increasingly sophisticated climate models.

Today few people deny the reality of climate change, although climate skeptics continue to refuse to acknowledge the weight of scientific evidence supporting the likelihood of global warming.

Is the Science Reliable?

In the decades of research into climate change, a handful of errors have emerged that have recently gained much media publicity.

Two instances of mistakes in climate science demonstrate the importance of solid research methods. The first example is the controversy around the 2007 IPCC report. This hugely influential document claimed that Himalayan glaciers were likely to disappear by 2035 if the world continued warming at its current rate. However this incorrect conclusion was based solely on the informal speculations by researcher, rather than on scientific method.

A second example is an article in Nature Geoscience in February 2010, which predicted that sea levels could rise by 7cm to 82cm 2100. The writers retracted their statements due to two mistakes in their mathematics. Nevertheless other studies have predicted similar rates of sea level rise.

Many commentators have taken these mistakes as evidence that climate change is not a real phenomena, but is instead a conspiracy cooked up by environmentalists and scientists.

However in response to these claims, many in the scientific community have highlighted that these few mistakes must be weighed against the overwhelming mass of evidence that supports the conclusion that climate change is actually happening.

For instance in the 2007 IPCC report, while mistakes were found in three of the conclusions, the report contained hundreds if not thousands of findings which have not been faulted. In addition, many scientific reports not produced by the Intergovernmental Panel on Climate Change support the findings of the IPCC.


All science is skeptical. Good science marshals the facts and proposes the most robust theory to explain them. Bad science or “pseudo-science” starts with a set of beliefs then selects the pieces of evidence which bolster that position.

The motivation behind bad science often lies in psychology or economics. Psychology may lead people to deny global warming because it is conceptually overwhelming, confusing, or contrary to their beliefs.

Economic interests motivate companies that profit from environmentally destructive behaviour to invest in research projects that refute aspects of climate science. For instance the key facts on climate change have routinely been denied by vested interests such as the coal industry and Exxon petroleum who fear a loss of income if the use of fossil fuels is curtailed.

Through their lobby groups, these companies have promoted various falsehoods about the science of climate change.

An exactly similar campaign was waged by tobacco companies, disputing the link between cigarettes and cancer. Sometimes the same lobbyists are employed.

As a result of their activities, a worrying amount of pseudo-science has muddied the water and seriously delayed global action on this issue.

A good place to start understanding the false science perpetrated by climate change skeptics is to understand common objections that they pose, and consider the logical scientific response.

A 25-page analysis of skeptics, their links and their activities, was compiled March 2010 by the environmental group Greenpeace. Clearly Greenpeace have their own agenda but the document is thoroughly referenced and well argued.

Or you can watch Prof Stephen Schneider expertly summarize the problem in 4 minutes!

Answers to Skeptics

Skeptics are a tricky bunch. You can talk to them about the urgent need to avert runaway climate change, and show them the IPCC reports compiled by 3000 of the world’s leading scientists, all describing the details of the impacts, contributing factors and solutions to climate change. And there’s no guarantee that they will believe you. Here are some common lines from the climate skeptics, and some ideas on how to respond.

If a skeptic tells you “climate change is a conspiracy theory”.

If a skeptic tells you ‘climate change is a conspiracy!’: Perhaps if they believe that tens of thousands of scientists are colluding in a massive conspiracy, then nothing anyone can say is likely to persuade them otherwise. So maybe you should end the conversation there. However if you’re feeling brave, then you could tell them that many scientists are instructed to tone down their findings by their sponsor. Also, it seems more likely that there is a conspiracy to silence scientists who gather evidence of global warming, as most researchers who challenge the science on climate change receive funding from major greenhouse-gas emitting companies.

When a skeptic says that ‘it’s cooler than before, so that disproves global warming’.

You can say that most cooling is short-term and confined to a few areas. By contrast, global warming is over the long-term, as the average global temperatures rise. As a result, the hottest years ever on record have all been in the last 12 years, and the long-term trend is unambiguously towards higher temperatures.

If a skeptic says that ‘global warming will be a good thing, it’s too cold where I live’.

You can tell them that while wealthy countries and individuals will be able to adapt to climate change in the short-term, simply by buying an air conditioner, in a decade or so, they might be eating their words. Not only is climate change already affecting millions today, it will devastate rich countries too. At more than 3 degrees Celsius of warming, most tropical and sub-tropical areas will be uninhabitable, and environmental refugees will be knocking at the doors of our air-conditioned houses.

When a skeptic says that ‘the human species is too small to change the climate’.

You can respond by saying that we are not the first species to radically change the face of the Earth. Think about plankton, which is the original source of the entire marine food chain, and was the organism that emitted enough oxygen for the Earth to support animal life. And just think about how much more capable we are than plankton. Not to mention that human migration has historically wiped out species and changed ecosystems all around the planet.

When a skeptic says that ‘global warming is caused by the sun’.

You can say that the sun emitted a third less energy about 4 billion years ago, yet for most of this time, the Earth has been even warmer than today. The reason: higher levels of greenhouse gases are trapping more of the sun’s heat.

When skeptics say that ‘Co2′ is not the worst greenhouse gas.

You can snap back that Co2 causes about 20% of the greenhouse effect. While the rest is due to water vapour and other greenhouses gases such as methane. However our Co2 emissions warm the Earth, triggering a positive feedback as the warming increases evaporation of water vapour from the oceans, and indirectly contributes enormously to the greenhouse effect.


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