According to a recent opinion poll conducted by Nielsen/Oxford University, global concern about climate change has decreased over the past two years. The survey, which included over 27,000 Internet users in 54 countries, revealed that 37 percent of respondents were "very concerned" about climate change, down from 41 percent in a similar poll two years ago. The decline in concern was attributed to the world economic slowdown. In the United States, the number of individuals who were very concerned about climate change dropped from 34 percent to 25 percent. President Barack Obama aims to reduce US greenhouse gas emissions, primarily from the burning of fossil fuels, and is set to participate in the Copenhagen meeting with over 100 world leaders in an attempt to secure a new UN agreement. China, the largest emitter of greenhouse gases, saw an increase in the number of people expressing serious concern, with 36 percent compared to the previous 30 percent. The survey revealed that Latin America and Asian-Pacific countries had the highest levels of concern, with the Philippines at the top with 78 percent, following the devastation caused by Typhoon Ketsana in September. The poll did not include most African countries. Conversely, those least worried about global warming, attributed to human emissions of greenhouse gases from burning fossil fuels, were primarily in eastern Europe. In Estonia, only 10 percent of people expressed a high level of concern about environmental issues, according to Jonathan Banks, Business Insights Director Europe of the Nielsen Co. However, with the upcoming Copenhagen summit, worries about climate change may be increasing. Despite economic concerns temporarily overshadowing environmental issues, the survey found that air and water pollution, followed by climate change, were the top three environmental concerns globally.