What is Climate Change

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We Are Changing Our Climate

Climate is usually defined as the “average weather” in a place. It includes patterns of temperature, precipitation (rain or snow), humidity, wind and seasons. Climate patterns play a fundamental role in shaping natural ecosystems, and the human economies and cultures that depend on them.

But the climate we’ve come to expect is not what it used to be, our climate is rapidly changing with disruptive impacts, and that change is progressing faster than any seen in the last 2,000 years.

The Earth's climate has changed on many timescales in response to natural factors. On long timescales, such as tens of thousands of years, we see the Earth move in and out of ice ages.

At the other extreme, El Ninos come and go every few years, temporarily raising the Earth’s temperature. Since we emerged from the last ice age around 11,000 years ago, the Earth’s climate has remained relatively stable, with global temperatures averaging at about 14°C.

However, in the last century our climate has started to change rapidly. The evidence points to a long-term change in our climate that is happening at an unusually quick rate. 1983-2012 was likely the warmest 30-year period of the last 1400 years.

Reconstruction of past temperature record and indication of current and future warming by Paul Price.

There are many factors that can cause a warming of our climate; for example, more energy from the sun, large natural events such as El Nino or an increased greenhouse effect. Scientists have ruled out the sun and natural variations in our climate as the major causes of the recent warming.

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. There is overwhelming evidence that the warming we’ve seen is due to increased amounts of greenhouse gases, such as water vapour, carbon dioxide and methane, in the atmosphere.

Human activities have directly increased the amount of carbon dioxide, methane and some other greenhouse gases. These increases can be through the burning of fossil fuels such as oil and coal, and changes in land use such as chopping down forests for cattle grazing.

"The science is unequivocal that humans are the cause of global warming, and major changes are already being observed: global mean warming is 0.8°C above pre industrial levels; oceans have warmed by 0.09°C since the 1950s and are acidifying; sea levels rose by about 20 cm since pre-industrial times and are now rising at 3.2 cm per decade; an exceptional number of extreme heat waves occurred in the last decade; major food crop growing areas are increasingly affected by drought."

- Dr. Jim Yong Kim
President, World Bank Group

 

Observed Changes to the Climate System

The effects of greenhouse gas emission–induced change on the climate system, reported by IPCC’s Fourth Assessment Report (AR4) in 2007, have continued to intensify, more or less unabated:

 The concentration of the main greenhouse gas, carbon dioxide (CO2), has increased by 40% from its preindustrial concentration of approximately 278 parts per million (ppm) to 391 ppm in 2013.

Concentrations of CO2, CH4, and N2O now substantially exceed the highest concentrations recorded in ice cores during the past 800,000 years.

Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energyaccumulated between 1971 and 2010.

 Global mean temperature has continued to increase and is now about 0.8°C above preindustrial levels.

Temperatures have been increasing and impacts are already being felt. Oceans have contineud to warm and have risen by 15 - 20 cm over the 20th century and continue to rise at 3.2 cm per decade. The warming of the atmosphere and oceans is leading to an accelerating loss of ice from the Greenland and Antarctic ice sheets, and this melting could add substantially to sea-level rise in the future. 

The effects of global warming are also leading to observed changes in many other climate and environmental aspects of the Earth system. The last decade has seen an exceptional number of extreme heat waves around the world with consequential severe impacts.

Preliminary estimates for the 2010 heat wave in Russia put the death toll at 55,000, annual crop failure at about 25 percent, burned areas at more than 1 million hectares, and economic losses at about US$15 billion (1 percent GDP). 

The area of the Earth’s land surface affected by drought has also likely increased substantially over the last 50 years, somewhat faster than projected by climate models. The 2012 drought in the United States impacted about 80 percent of agricultural land, making it the most severe drought since the 1950s. Negative effects of higher temperatures have been observed on agricultural production, with recent studies indicating that since the 1980s global maize and wheat production may have been reduced significantly compared to a case without climate change.

"I got it wrong on climate change - it's far, far worse"

- Lord Nicholas Stern
Climate Change Economist

Preventing a 2° Warmer World

"Despite the global community’s best intentions to keep global warming below a 2°C increase above pre-industrial climate, higher levels of warming are increasingly likely. Scientists agree that countries’ current United Nations Framework Convention on Climate Change emission pledges and commitments would most likely result in 3.5 to 4°C warming. And the longer those pledges remain unmet, the more likely a 4°C world becomes."

 

- Dr. Jim Yong Kim
President, World Bank Group

The global community has committed itself to holding warming below 2°C to prevent “dangerous” climate change, and Small Island Developing states and Least Developed Countries have identified global warming of 1.5°C as warming above which there would be serious threats to their own development and, in some cases, survival.

However, the sum total of current policies – in place and pledged – will very likely lead to warming far in excess of these levels. Indeed, present emission trends put the world plausibly on a path toward 4°C warming within the century.

A world in which warming reaches 4°C above preindustrial levels, would be one of unprecedented heat waves, severe drought, and major floods in many regions, with serious impacts on human systems, ecosystems, and associated services.

Warming of 4°C can still be avoided: numerous studies show that there are technically and economically feasible emissions pathways to hold warming likely below 2°C. Thus the level of impacts that developing countries and the rest of the world experience will be a result of government, private sector, and civil society decisions and choices, including, unfortunately, inaction.

"We can choose to believe in the overwhelming judgement of science and act before it's too late."

- Barack Obama

Tacking Action on the Climate Challenge

"We can help cities grow clean and climate resilient, develop climate smart agriculture practices, and find innovative ways to improve both energy efficiency and the performance of renewable energies. We can work with countries to roll back harmful fossil fuel subsidies and help put the policies in place that will eventually lead to a stable price on carbon. We are determined to work with countries to find solutions. But the science is clear."

- Dr. Jim Yong Kim
President, World Bank Group

Climate change is already undermining progress and prospects for development and threatens to deepen vulnerabilities and erode hard-won gains. Consequences are already being felt on every continent and in every sector. Species are being lost, lands are being inundated, and livelihoods are being threatened. More droughts, more floods, more strong storms, and more forest fires are taxing individuals, businesses and governments. Climate-related extreme events can push households below the poverty trap threshold, which could lead to greater rural-urban migration. Promoting economic growth and the eradication of poverty and inequality will thus be an increasingly challenging task under future climate change.

Actions must be taken to mitigate the pace of climate change and to adapt to the impacts already felt today. It will be impossible to lift the poorest on the planet out of poverty if climate change proceeds unchecked. Strong and decisive action must be taken to avoid a 4°C world – one that is unmanageable and laden with unprecedented heat waves and increased human suffering. It is not too late to hold warming near 2°C, and build resilience to temperatures and other climate impacts that are expected to still pose significant risks to agriculture, water resources, coastal infrastructure, and human health. A new momentum is needed. Dramatic technological change, steadfast and visionary political will, and international cooperation are required to change the trajectory of climate change and to protect people and ecosystems. The window for holding warming below 2°C and avoiding a 4°C world is closing rapidly, and the time to act is now.

Climate Change Links

There are a number of great online resources that all show the overwhelming scientific consensus that climate change is happening, that it is due to human-caused emissions of greenhouse gases and that we are already experiencing the impacts. The following are a few:

NASA's climate change portal

US Environmental Protection Agency climate change portal

Nature Journal Climate Change

Intergovernmental Panel on Climate Change

Skeptical Science - Getting skeptical about global warming skepticism

The Tree - Content for Climate and Energy Communicators

Climatica - Youth and Experts Exploring Climate Science

ClimateComms - mapping news and information on climate change in the US

World Resources Institute CAIT Climate Data Exporer

World Bank Group climate change portal

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Blogs
  • Years of Living Dangerously Launch at World Bank

    April 12 2014

    A Special Preview of the documentary mini-series Years of Living Dangerously and Discussion on Climate Change was arranged by Connect4Climate. “I hope the stories here will be a wake-up call” - World Bank Group President Jim Yong Kim.

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    April 07 2014

    VIP screening of Showtime’s new documentary mini-series Years of Living Dangerously and panel discussion will highlight the challenges posed by climate change. World Bank Group President Jim Yong Kim will open the event, followed by a panel discussion with Climate Change Group Vice President Rachel Kyte, New York Times Columnist Thomas Friedman and leading global conservation scientist Dr. M. Sanjayan.

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