OTTAWA — The economic impact of climate change on Canada could climb to billions of dollars per year, according to a study published Thursday by a policy group that advises the Canadian government. The report "Paying the Price: The Economic Impacts of Climate Change for Canada" by the National Round Table on the Environment and the Economy estimates that warming-related costs may rise to $5 billion per year by 2020, and between $21 and $43 billion per year by 2050. It points to a reduced timber supply, storm surges and flood damage due to rising sea levels in coastal areas and poorer air quality in cities leading to more hospital visits. And it calls on Ottawa to invest more in generating and disseminating research and detailed analysis to help communities adapt to climate change to try to avoid some of the added costs. Canada contributes less than 1.5 percent of global carbon emissions. However, "increasing greenhouse gas emissions worldwide will exert a growing economic impact on our own country, exacting a rising price from Canadians as climate change impacts occur here at home," the study said. "Climate change will be expensive for Canada and Canadians." For example, warmer temperatures and higher levels of carbon dioxide in the atmosphere may accelerate forest growth in some areas. However, the gains are expected to be more than offset by tree losses from increased forest fires, pests and extreme weather events including wind and ice storms. Canada is home to almost 3.5 million square kilometers of forests, representing 10 percent of global forest cover. The forestry industry drives 1.7 percent of Canada's gross domestic product. Losses in the sector due to climate change, the study concluded, could rise to $17 billion per year, with westernmost British Columbia province's forest-reliant economy likely suffering the most. Low-lying and highly dense areas on the Pacific Coast, such as Vancouver, and Arctic regions such as Nunavut (which are experiencing the most dramatic rise in temperatures) also face the highest per capita costs of dwelling damage due to flooding, it said. But the coastal areas of Prince Edward Island in the Atlantic Ocean are most at risk, said the report. Flooding costs nationwide could top eight billion dollars per year by 2050, it concluded. Finally, big cities such as Toronto and Vancouver are expected to experience more summer heat spells and worse air quality over the coming years, leading to more cardiovascular and respiratory woes. Nationwide, fewer extreme cold days could reduce overall illnesses and deaths in winter, said the report. But some populations will face a greater risk of exposure to infectious diseases and diseases transmitted through water and food. The magnitude of costs, it said, will depend on global emissions growth and Canadian economic and population growth.