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The U.N. answers your climate questions

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(CNN) -- Yvo de Boer, the Executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC), hast fielded questions exclusively from CNN.com users on the environmental issues that matter to you. De Boer is the United Nations' top official on climate change.

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Yvo de Boer

CNN reserves the right to edit submitted material for the sake of length, grammar and clarity.

QUESTION NO. 1:

I understand that the Southern and Northern Hemisphere Atmospheres do not mix very much across the equator so the Southern Atmosphere, covering less well developed countries, should have less carbon dioxide in it. If this is so is it not appropriate for the Southern Hemisphere countries to have no targets for CO2 reduction until those in the North and South are equal? And has anyone done the economic models to determine whether it would be cheaper to simply prepare for inevitable climate change rather than try to reduce atmospheric CO2?
Geoff Handley, Australia

De Boer:

Dear Mr. Handley,

The United Nations Framework Convention on Climate Change (UNFCCC) is based on the principle of "common but differentiated responsibilities," which in essence refers to the fact that certain problems affect and are affected by all nations in common, if not to the same degree; and that the resulting 'responsibilities' ought to be differentiated because not all nations should contribute equally to alleviate the problem.

Within the intergovernmental process on climate change under the UNFCCC, this relates mainly to the fact that industrialized developed countries need to take the lead in addressing climate change, specifically excluding developing countries from binding greenhouse gas (GHG) emissions reductions. The differentiation does thus not occur according to hemisphere, but rather according to historical responsibility of industrialized nations and their capacity to act.

The latest scientific findings of the Intergovernmental Panel on Climate Change (IPCC) established beyond doubt that climate change is happening and that much of it is caused by human activity.

Over the last three decades, greenhouse gas emissions increased by an average of 1.6 percent per year with CO2 emissions from fossil fuels use growing at 1.9 percent per year. For the period 1970-2004, the largest growth in greenhouse gas emissions has come from energy supply and road transport.

Warming during the past 100 years was 0.74 degrees Celsius, with most of the warming occurring in the past 50 years. The warming for the next 20 years is projected to be 0.2 degrees Celsius per decade. The world faces an average temperature rise of around 3°C this century if greenhouse gas emissions continue to rise at their current pace and are allowed to double from their pre-industrial level.

To put this into perspective: if the global temperature increase exceeds 1.5-2.5 degrees Celsius, there is an increased risk of extinction of 20-30 percent of plant and animal species, increased risk of water shortages and hunger for millions of people and extreme weather events such as heat waves, droughts and floods. Emissions thus need to be reduced urgently.

At the same time, access to energy is one of the over-riding developmental concerns of developing countries, especially for economic growth. According to the reference scenario of the International Energy Agency (IEA), global energy demand will grow by 60 percent by 2030. In the period up to 2030, the energy supply infrastructure world-wide will require a total investment of $20 trillion, with more than half of that in developing countries.

The way in which these energy needs are met will determine whether climate change will remain manageable. Both national and international climate policies and actions need to globally green energy supply and economic growth. It is of paramount importance that the growth of emissions is decoupled from economic growth.

On your second question:

Numerous studies have examined the cost of climate change. All studies concur that the cost of inaction by far outweighs the cost of action.

One of these studies, the Stern Review, concludes that mitigation - taking strong action to reduce emissions - must be viewed as an investment, a cost incurred now and in the coming few decades to avoid the risks of very severe consequences in the future.

Based one numerous economic models, the Stern Review's findings show that ignoring climate change will eventually damage economic growth. Our actions over the coming few decades could create risks of major disruption to economic and social activity, later in this century and in the next, on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century. And it will be difficult or impossible to reverse these changes. Tackling climate change is the pro-growth strategy for the longer term, and it can be done in a way that does not cap the aspirations for growth of rich or poor countries. The earlier effective action is taken, the less costly it will be.

However, the climate system is characterized by inertia and does not immediately respond to reductions in greenhouse gas emissions. Some greenhouse gases survive in the atmosphere for years, decades or even centuries. As a result, climate change will continue for hundreds of years after atmospheric concentrations have stabilized.

Given that climate change is already happening, and that its impacts will become increasingly evident as the inertia gives way, measures to help people adapt to it are essential. The less mitigation we do now, the greater the difficulty of continuing to adapt in future and the costlier adaptation will become.

Adaptation and mitigation should thus not be viewed as competing concepts. It is of utmost importance that they be accorded equal importance in the response to climate change.

QUESTION NO. 2:

What is response about the upcoming Climate Change meeting of the countries at Washington this week and do you see this as a challenge to the existing system?
Tirthankar Mandal New Delhi, India

De Boer:

Dear Tirthankar Mandal

Many thanks for your interest.

The Major Economies Meeting (MEM) took place in Washington on 27-28 September 2007. The chair's summary of the meeting clearly emphasized the centrality of the U.N. in addressing climate change on a global level and that the MEM initiative -- to be completed in 2008 -- intends to provide a detailed contribution to the process under the United Nations Framework Convention on Climate Change (UNFCCC). This point was also repeatedly made by high-level US officials, as well as by President Bush in his address to the meeting. The initiative is thus not perceived as a challenge to the UN's intergovernmental climate change process. The US seems intent on making a valuable contribution to the UNFCCC process, which is encouraging.

The economic cost of delayed and fragmented action will by far exceed the economic cost of taking early, strong and concerted action. Strong action on climate change is necessary to avoid the dramatic consequences of accelerated environmental deterioration and the societal consequences, particularly for the poorest and most vulnerable. There is a need for real action on a global level that measures up to what science is telling us.

The MEM clarified that U.S. President George W. Bush wants to focus on technology cooperation to draw climate-friendly technologies into the market. He wants to offer voluntary targets at the national level, whereby the U.S. is committed to writing that national target into legislation.

There was a very frank discussion at the MEM about the nature of emission reduction targets. I found it interesting that nearly all of the private sector participants indicated that the private sector does need a clear sense of direction, and many pointed to legally binding targets and caps as being essential.

A response to climate change can only be successful if it entails industrialized countries continuing to take the lead in emission reductions, and going well beyond present efforts, given their historic responsibility and their economic capabilities. This is a principle in the UNFCCC and has evolved to involves caps for industrialized countries. It is difficult to see how the carbon market - spawned by the Kyoto Protocol and a tool for cost-effective emission reductions - would work without caps. Plus the question is, how credible a purely voluntary scheme would be at the international level. I think that the Kyoto Protocol draws a great part of its credibility from the fact that it is legally binding.

The Europeans and many developing countries are putting the central emphasis on a system which is driven by caps. If targets are written into national legislation, then that is more robust than if it is of a purely voluntary nature. The first round of commitments under the Convention showed that if you have something that is purely aspirational, you have no guarantees that countries will really work towards reaching that goal. The more you ratchet up the formality, the greater the possibility that real emission reductions will be achieved. The more industrialized countries agree to caps, the greater the cost-effective emission reduction yields through the carbon market.

QUESTION NO. 3:

I'm working on a book about global youth viewpoints. One of their major concerns is global warming and pollution of the environment. What can young people do to help solve this problem? Thanks,
Gayle Kimball, Chico, California, USA

De Boer:

Dear Gayle Kimball

Your book sounds like an excellent initiative! Given that climate change is a long-term problem, which requires a long-term response, young people need to be involved in solving this problem. There are many things that young people can do. In my opinion, this includes:

  • If they have not yet done so, change their behavior to use energy sparingly. They should switch off lights that are not needed, not leave electrical appliances on 'stand-by' mode, only buy energy-efficient technological products and use energy-efficient light bulbs.
  • If they drive cars, they can try to drive environmentally friendly cars or form car-pools, where possible.
  • MTV's "Switch!" campaign is a valuable source of information on practical things that we can all do, that is aimed at young people.
  • They need to inform peers who are less knowledgeable on the topic to increase awareness for climate change and its impacts.
  • They could try to make climate change and environment a topic of discussion at school to increase awareness of impacts and for solutions.
  • They could urge policy-makers to translate science into policy for the sake of their future.
  • QUESTION NO. 4:

    Dear Sir:

    What percentage of climate change processes can be attributed to industrial pollutants as compared to natural processes, including those that are attributed to domesticated and wild animal methane releases, volcanic eruptions, increase heat from the sun, natural warming from plant decay, etc?

    Natural warming/glacier melting has been occurring for millennia, it will not change no matter what we do. Why not focus on adapting to changes that are inevitable? I don't suggest that we shouldn't be environmentally friendly, just that climate change is coming and we should prepare for that before it is too late.
    Korey Dykstra, Canada

    De Boer:

    Dear Korey Dykstra,

    The increased levels of greenhouse gases have caused the most dramatic change in the atmosphere's composition since at least 650,000 years ago.

    Carbon dioxide is the largest contributing gas to the greenhouse effect and levels appear to have varied by less than 10 percent during the 10,000 years before industrialization. Over the past 200 years levels have risen by over 30 percent. Even with half of humanity's carbon dioxide emissions being absorbed by the oceans and land vegetation, atmospheric levels continue to rise.

    The climate system is characterized by inertia and does not immediately respond to reductions in greenhouse gas emissions. Some greenhouse gases survive in the atmosphere for years, decades or even centuries. As a result, climate change will continue for hundreds of years after atmospheric concentrations have stabilized. Notwithstanding this, human-induced climate change has caused the climate to change so rapidly compared to natural climatic changes, that ecosystems and natural systems are unable to keep up in terms of evolving along with it.

    Adapting refers to minimizing the negative consequences of climate change on peoples' lives, as well as galvanizing the possible positive consequences. Adaptation is a process through which societies make themselves better able to cope with an uncertain future.

    Adaptation options are many and range from technological options such as increased sea defenses or flood-proof houses on stilts, to behavior change at the individual level, such as the sparing use of water in times of drought.

    In the context of future international policy, adaptation does not replace mitigation of greenhouse gas emissions. On the contrary, both adaptation and mitigation need to follow parallel tracks during the same period of time, thus complementing each other. The less mitigation we do now, the greater the difficulty of continuing to adapt in future and the costlier adaptation will become. Emissions clearly need to be reduced urgently.

    QUESTION NO. 5:

    I am an Australian living in Tasmania. Could you please advise me on the following:

    A) Exactly how accurate is the modeling for each of the variables that affect the Earth's climate and what is the level of mathematical uncertainty attached to them when used collectively to model projected changes in the earth's climate for the next 100 years?

    B) What level of uncertainty (mathematically speaking) is attached to the IPCC's estimates for changes in temperature and sea level for the Earth through to the years 2125, 2150, 2175 and 2100?

    C) Which countries in the northern and southern hemispheres are undergoing Isostatic uplift and what is the value of this uplift (for each of them) relative to the IPCC's estimates for global sea level rises to the year 2100?

    I look forward to receiving your response. Best of luck with your work. Kind regards,
    Greg Lear, Tasmania, Australia

    De Boer:

    Dear Mr. Lear,

    Colleagues of the IPCC Secretariat in Geneva have kindly provided the answers to these technical questions.

    On question A: All Essential Climate Variables are interconnected. The accuracy of modeling for temperature is the highest because temperatures have been recorded regularly since basically 1861 and modeling has been thoroughly verified. The modeling of temperature with and without greenhouse gases and other influences has shown that the curves of observed and modeled temperature almost coincided with deviations of the order of tenths of a degree on a global scale. Limitations of models and uncertainties of scenarios produce nearly the same range of expected errors, which are of the order of a degree or two for a projection up to 2100. What is significantly less certain is regional change. This requires additional research and effort on the regional downscaling of global projections. This important to enable adaptation to climate change.

    On question B: The level of uncertainty for surface temperature was covered in the previous answer. The IPCC has determined the level for sea-level rise noting uncertainties associated with every factor contributing to the phenomenon. The level of uncertainty for sea-level rise estimates for 2025, 2050, 2075, and 2100 depends on the uncertainty in warming and also some other factors. Comprehensive regional and time-sliced projections are in the process of being produced. For a recent update on understanding the uncertainties and how to address them, please go to http://wcrp.ipsl.jussieu.fr/Workshops/SeaLevel/Reports/Summary_Statement_2006_1004.pdf

    On question C: The mean sea surface will change because of ongoing glacial isostatic adjustment (GIA)-induced deformations which change the shape of the ocean basin. As an example, the collapsing forebulge caused by the last glaciation would extend into the ocean off the North American east coast. Globally averaged over the oceans, this effect has a non-zero contribution to the sea surface. Overall, the changing shape of the ocean basins due to GIA causes the mean sea surface to decrease by about 0.3 millimeters per year. Estimates of sea-level rise from altimetry will increase by roughly this amount once the GIA contribution is removed. The pattern of the GIA effect is complicated, with many countries affected. E-mail to a friend E-mail to a friend

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