(CNN) -- Procrastinate on tackling a problem and it might get worse, and more expensive. Climate change is no different, a new report says.
The longer we wait to mitigate the detrimental levels of carbon dioxide thrown into the atmosphere, the harder it's going to be to work against rising temperatures, says a leaked draft report from the United Nations Intergovernmental Panel on Climate Change, obtained by CNN.
"It's really about cars and coal," said Marilyn Brown, professor of public policy at Georgia Institute of Technology, who was one of the review editors of the report. "We need to reduce our reliance on coal power and find a way to transport ourselves and all of the goods we consume more economically, more efficiently."
Climate experts have modeled a variety of scenarios of how atmospheric carbon dioxide concentrations will affect global temperature changes. If in 2100 the atmospheric carbon dioxide levels are between 430 and 480 parts per million, the global temperature change, as compared to the mid-1800s, will be likely to stay below 2 degrees Celsius, according to a chart in the report.
A greater temperature change becomes more likely if carbon dioxide levels exceed 530 ppm by 2100.
Already, in 2013, atmospheric carbon dioxide reached a historic high of 400 ppm at the National Oceanic and Atmospheric Administration observatory in Mauna Loa, Hawaii.
"Delaying mitigation through 2030 will increase the challenges of, and reduce the options for, bringing atmospheric concentration levels to 530 ppm" or lower by the end of the century," the report said.
Two degrees Celsius may seem tiny, but a U.N. report from September said that a rise of 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of this century could result in "a nearly ice-free Arctic Ocean in late summer."
Carbon dioxide changes climate and drives acidification of the ocean. Rising temperatures boost sea levels and increase the likelihood of extreme storms. Agriculture, forestry, ecosystems and human health are all expected to suffer as a result of trends in climate change.
The September U.N. Intergovernmental Panel on Climate Change report said there is 95% certainty that rising temperatures are due to human activity.
The newer report's draft is dated December 17, and the wording may change between now and when the finalized report is released from Yokohama, Japan in late March.
The two main drivers of increases in fossil fuel carbon dioxide emissions from 2000 to 2010 were economic and population growth, the latest report draft said. Over the same time period, there has been an increased use of coal relative to other energy sources.
Here's a U.S. perspective on that: Coal-fired electricity generation represented 37% of total generation in 2012, according to the U.S. Department of Energy.
Coal use for generating electricity is a big part of why carbon dioxide emissions have nearly doubled their rate of growth worldwide, the report said. The growth rate was 1.3% per year from 1970 to 2000, and 2.2% per year from 2000 to 2010.
If there aren't explicit efforts to reduce greenhouse gas emissions, the drivers of emissions growth are projected to continue, regardless of improvements in energy supply and technology, the report said.
Ten countries were responsible for 70% of carbon dioxide emissions from fossil fuel combustion and industrial processes, the report said.
Climate experts have come up with models of various scenarios of what would happen at various atmospheric concentrations of carbon dioxide.
"Limiting peak atmospheric concentrations over the course of the century -- not only reaching long-term concentration levels -- is critical for limiting temperature change," the report said.
Another problematic piece in the climate change puzzle is fossil fuel subsidies, which provide incentives for people to consume high carbon-dioxide emitting fuels. Brown noted that countries such as Russia, Nigeria, and many Middle Eastern nations sell gasoline and natural gas to citizens at a discount.
Worldwide, such subsidies totaled $544 billion in 2012, according to the International Energy Agency.
"Reduction of subsidies to fossil fuels can achieve significant emission reductions at negative social cost," the draft report said.
There are also efforts to incentivize clean energy, however. China is producing cheap solar power technologies because the government subsidizes solar manufacturing companies, Brown said.
Many renewable energy technologies have progressed in their performance and cost, and this form of energy is fast-growing, the report said. But in order to increase their market share, such technologies need support.
Nuclear energy is low in greenhouse gas emissions, but since 1993 its share of electricity generation worldwide has been declining, the report noted. Concerns about operational safety, security of waste management and proliferation of nuclear weapons are some of the main reasons that nuclear power isn't thriving. New technologies that target some of the concerns are in the works.
Another potential tool against fossil fuel emissions are carbon capture and storage technologies, which suck carbon dioxide out of the air and store it, often underground. But as of now, they are quite costly, Brown said.
Some countries have implemented carbon taxes; combined with technology and other policies, such efforts have led to a "decoupling of carbon emissions from GDP," the report said.
The report gives attention to the programs and policies that developing countries can use in particular to mitigate carbon dioxide emissions.
"It's in the developing world where we're seeing such an acceleration of CO2 emissions," Brown said. "Our focus needs to address them more directly in the future."
Country-specific targets known as the Cancun Pledges include emissions that are too high to keep atmospheric carbon dioxide between 430 and 530 parts per million by 2100, and delay mitigation through 2020, the report said. But delaying until 2030 would be even more costly, economically and in terms of actually making a substantial impact with current technology.
The message is clear: Delay more, pay more -- or it might be too late.
CNN's Brandon Miller contributed to this report