In releasing the first part of its fifth assessment report on Sept. 27, the Intergovernmental Panel on Climate Change said that temperatures are likely to rise by 0.3 to 4.8 degrees Celsius and sea levels could rise by 26 to 82 cm by the end of the 21st century compared with the latest 20 years.

The report, which follows one released in 2007, said that as greenhouse gases continue to accumulate in the atmosphere, more heat waves, floods and droughts will take place, and sea levels will rise as oceans warm and glaciers and ice sheets melt.

The IPCC is scheduled to release a series of four additional reports from this year to autumn of next year, including a report on the effects of global warming on people’s lives and ecosystems.

It is clear what governments must do to prevent the disastrous effects of climate change: reduce emissions of greenhouse gases by shifting toward greener energy sources. But the international community has failed to adequately respond to the warnings that scientists have been making and to take necessary actions in a timely manner.

Japan’s efforts to fight global warming have flagged in recent years. The Abe administration in particular has done virtually nothing to reduce greenhouse gas emissions and promote renewable green energy. The Japanese government must take the latest report seriously and start taking concrete efforts immediately. Prime Minister Shinzo Abe and other government leaders concerned must change their business-as-usual outlook and become serious about tackling climate change.

According to the report, the world’s average temperature rose by 0.85 degree Celsius between 1880 and 2012, and the world’s average sea level rose by 19 cm between 1901 and 2010. Sea levels have likely risen by an average 3.2 millimeters per year between 1993 and 2010. It also warned that concentrations of carbon dioxide, methane and dinitrogen oxide in the atmosphere have reached unprecedented levels in the past 800,000 years, and that because oceans absorb 30 percent of carbon dioxide attributable to human activities, they are becoming more acidic.

The report stated that scientists are 95 percent certain that human activities have been the main cause of climate change since the mid-20th century. Although the report admitted that there has been a hiatus in global warming in this century — slower temperature rises despite growing emissions and the Arctic ice cap expanding by 29 percent in the past year — it stated that the phenomenon is a natural variation that would not last.

Succinctly summarizing the message of the report, Mr. Achim Steiner, executive director of the U.N. Environment Program (UNEP), said, “Climate change is a long-term challenge but one that requires urgent action — not tomorrow but today and right now — given the pace and the scale by which greenhouse gases are accumulating in the atmosphere and the rising risks of a more than 2-degree Celsius temperature rise.”

It is regrettable that data since 1990 — the year when the IPCC released its first report — show that Japan’s efforts to tackle global warming have stagnated. Although Japan’s economic growth has slowed down and its population is shrinking, its emissions of carbon dioxide due to energy use have increased by about 10 percent, resulting in an increase in the average amount of carbon dioxide emitted per capita. Japan’s edge in energy saving over other nations has become almost nil as Europe has caught up with Japan in its efforts to reduce CO2 emissions for every unit of gross domestic product. In the meantime, per capita CO2 emissions in the United States have fallen and its total emissions are rapidly decreasing.

The contrast between Japan and Germany is stark. Germany, the world’s No. 4 economy, has managed to grow economically while greatly reducing CO2 emissions through the expansion of green energy sources and energy savings.

Japan, meanwhile, has failed to introduce strong energy saving regulations and emissions trading, and was slow to start imposing a carbon tax. It has also taken few steps to promote green energy. So when Japan was forced to shut down its nuclear reactors in the wake of 3/11, it had no choice but to expand its thermal power generation, including the burning of coal.

On May 30, 2011, following the nuclear crisis at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant, Germany decided to abandon nuclear power within 11 years. Since then it has accelerated the expansion of renewable energy sources and strengthened its energy saving measures. Meanwhile, moves toward a carbonless society in Japan have stalled and its economy is suffering from rises in the prices of imported energy resources.

Political and business leaders in Japan have failed to recognize that measures designed to reduce CO2 emissions are an investment in the future. They are obsessed with the idea that such measures are an economic burden. But measures to reduce CO2 emission boost international competitiveness because they promote the efficient use of available resources and minimize the release of industrial waste, which takes a costly toll on the environment and people’s health.

Japan must carry out the following measures in earnest: strengthen efforts to conserve energy, expand emissions-trading and carbon-tax measures, improve the system under which major power companies purchase electricity generated from renewable energy sources at fixed prices, and separate electricity distribution from major power companies, which now monopolize both electricity generation and distribution. The latter measure would help encourage entry into the market by companies that will generate electricity from renewable resources.

Japan is now paying dearly for its lack of effort to reduce its reliance on fossil fuels. Since it is clear what Japan must do, its political leaders should stop listing reasons for doing nothing and instead take decisive steps forward.

Only when Japan begins to take concrete actions at home can it make meaningful contributions in the international community’s ongoing discussions on forming a new framework to fight climate change. Talks on the content of the framework must be concluded by the end of 2015, and the framework is scheduled to start in 2020. Japan’s political leaders must realize that little time is left and begin to take action now.