Human-induced changes in long-term weather averages and new variability—with extremes such as droughts, severe storms and floods—that are being observed and are projected to continue.

Climate change is happening, and it's happening now. It's not just a phenomenon that will happen in some unknown future, and it's not only about hotter temperatures. In some parts of the world annual rainfall is expected to decrease over the long term; in other places, new fluctuations in rainfall and temperatures will have a serious impact. Even where annual rainfall stays the same, it may rain after bigger gaps in time, or rain much harder and for shorter periods. This could lead to both increased droughts and increased flooding. The intensity of severe storms such as hurricanes could also increase. The potential impacts of climate change are far-flung and varied, and addressing it has become a top priority for today's global development agenda.

Although Earth's climate has fluctuated over history, in the last 100 years this has happened at a rate like never before, with average surface temperature rising by about 0.6-0.7ºC (1.2 to 1.4ºF). It may not sound like much, but since climate is a "non-linear" dynamical system, even slight temperature changes have a range of cascading effects (scientists associated with the IPCC are continually trying to model these to predict future climate). The eight warmest years since 1850 have all occurred after 1998, the warmest being 2005.

Humans are causing this. By burning fossil fuels such as oil, coal and gas, and clearing forests we have drastically increased the amount of carbon dioxide (CO2) and other greenhouse gases in the atmosphere. More of these gases means that less heat can escape into space. While the greenhouse effect occurs naturally—making Earth warm enough to inhabit—human activity since the Industrial Revolution of the late 18th century, has created a "runaway greenhouse effect," accelerating global warming. Today, atmospheric CO2 is at a level that has not been seen for at least 800,000 years!

Climate change is a development issue. Because of its potential to affect so many aspects of human life, it is arguably the world's most important development issue today. The world's rich countries, which industrialized many decades ago, are largely responsible for setting the problem in motion. But the poorest communities and countries will be hardest hit, since they are typically more vulnerable to increased floods, droughts, storms, and other climatic changes, and don't have the means to cope adequately. Many development gains could even be reversed because of climate change, leaving more people in poverty. Climate change is expected to:

• Damage agriculture and threaten the food supply. 
• Reduce water supplies and quality.
• Lead to more malaria, dengue fever and other diseases, raising death tolls where health services are already weak.
• Harm ecological systems and reduce biodiversity.
• Raise sea levels, displacing millions of people and even threatening the existence of some low-lying island states.

The international community recognizes that climate change will affect poor people. Scientists, policymakers and societies are tackling the issue on several fronts. 

Adaptation 

Adaptation means taking measures to prepare for the impacts of climate change. This includes education, awareness-raising and training on the impacts of climate change, as well as actions such as planting drought-resistant seeds, and creating better coastal protection. People's ability to adapt is influenced by their income, health, access to secure shelter, social networks, and local policies. Sound development policies should consider adaptation needs, and countries are increasingly doing so. Climate change is already threatening the lives, health and livelihoods of hundreds of millions worldwide. Many of these people lack the financial, technical, human and institutional resources to adapt.

An important first step toward adaptation is identifying who is most affected and how. This knowledge helps shape strategic planning for adaptation at all levels, from the global to the local.

Mitigation

Mitigation means actions that will reduce the production of greenhouse gas emissions or remove them from the atmosphere. We can lower emissions by using fewer fossil fuels for energy production and more alternative energy sources such as solar, wind and hydropower. Trees remove carbon dioxide from the atmosphere and absorb carbon, which is why planting forests is great. Deforestation, on the other hand, often releases carbon back to the atmosphere. Even though developed countries have been largely responsible for causing climate change, rapid industrialization in developing countries is deepening the damage, mainly as they cut down forests and use more fossil fuels. The big challenge today is for these countries to develop without adding to the environmental harm triggered by today's industrialized nations.

In 2008, the World Bank, other multilateral development banks, and a range of developed and developing countries created the Climate Investment Funds (CIF).  The goal is to help developing countries adapt to, and mitigate the effects of climate change.  Specific funds within CIF are aimed at increasing investment in low-carbon technologies, and supporting innovative programs that address climate change.  At this point, donors have pledged $6 billion to the CIF.

Each of us, no matter where we live, can help reduce carbon emissions at an individual level. You can recycle more, walk, or ride a bike instead of driving and unplug idle electronics—there is much more you can do (see this UNEP fact sheet). These may seem like small steps, but they do make a difference, especially when whole communities take these steps.
           
Spreading the word is another important way to make an impact. Many people aren't aware of the urgency of the climate crisis, and knowing more may spur them into action too.

Check out the Learn More box on this page, and share what you learn with your friends and family.