Evidence of climate change

Changes in the atmosphere, the oceans and glaciers and ice caps now show unequivocally that the world is warming due to human activities, the Intergovernmental Panel on Climate Change (IPCC) said in report released in November 2007.

The Synthesis Report (AR4) was published on Saturday 17 November 2007.

The report is a landmark with respect to the positive messages about the potential to deal with climate change both in the short and long term. It concluded the following:

• Warming of the climate system is unequivocal and the role of human activities in the observed changes is now clearer than ever. The world is already committed to further warming from past emissions alone.

• The net effect of greenhouse gases and aerosols due to human activities since the pre-industrial era is one of warming (+1.6 Wm-2). This is substantially greater than natural warming or cooling effects over the same period, due to solar changes and volcanoes.

• In the absence of effective international effort, GHG emissions will continue to grow rapidly over the coming decades. On current projections, this would result in a warming of between 1.7°C and 4.0°C by 2100 dependent on the level of emissions.

• Rising temperatures will be accompanied by many other changes to the Earth system, affecting food and water supplies, human health, biodiversity and the economy. All areas of the world will be affected, although the scale of impacts will vary considerably by region and depend on the existing vulnerability. The extent and severity of negative impacts will rise with temperatures, as will the risk of triggering major effects over which we have no control. We now have better estimates of the magnitude of these effects.

• An important new finding is the observed and projected ocean acidification due to increased carbon dioxide concentration.

• The report identifies five strong “reasons for concern” for the international community to take note of. These include the fact of new and stronger evidence about the risks to specific communities and systems, higher levels of vulnerability to extreme weather events; stronger evidence that the poorest countries will be most vulnerable to climate change; that the risks of large-scale, irreversible events could hit the world if we continue as we are; and the fact that all these point to the likely costs to our global economy from climate change being higher than ever- confirming the findings of the Stern Review, that the costs of inaction and postponing outweigh the costs of action.

• A portfolio of adaptation and mitigation measures can reduce the overall risks associated with climate change. Adaptation is essential to reduce the effects of climatic changes and is the only means to respond to the impacts from historic emissions. But there are limits to what adaptation can deliver. Mitigation is the only way to curb climate change.

• Global emissions must peak in the next decade or two and then decline to well below current levels by the middle of the century if we are to avoid dangerous climate change. This is economically and technically feasible, and can be achieved with technologies available now. Postponing action to cut GHGs will make it more difficult and costly to reduce emissions in the future, as well as creating higher risks of severe climate change impacts.

• All sectors can contribute to cost-effective emissions reductions, but a mix of policy instruments will be required to make the most of this potential.

• Our actions in the next decade will have a large impact on opportunities to avoid dangerous changes. Low carbon technologies are available, but without global agreements on emissions and the introduction of effective policies to put technologies in place, GHG will increase rapidly. Putting a price on carbon, so that polluters pay the price of their emissions, is critical. Governments must also invest more in energy RD&D to deliver technologies that supply the growing demand without emitting GHGs.

Green Shoots Media work in partnership with the Carbon Advice Group to help indivuals and organisations to become more informed about Green issues.

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