Fifth Time is the Charm: The Definitive Word on Climate Science
Posted September 27, 2013
The first Intergovernmental Panel on Climate Change (IPCC) report was released outside London in 1990. It concluded that carbon dioxide and other heat-trapping gases would cause unprecedented climate change if nothing were done to reduce emissions. Some global warming had already been observed, but at the time scientists didn’t have enough data to attribute that warming to atmospheric pollution. Now they do.
In its fifth assessment report, released earlier today in Stockholm, the world's leading climate scientists reported a consensus that there is at least a 95 percent probability that burning fossil fuels is causing climate change.
"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia," the report finds.
The message couldn't be more clear: we have to reduce our reliance on coal, gas and oil, and cut the carbon pollution that is driving climate disruption.
There has been a lot of talk about addressing climate change since the first IPCC assessment, but not nearly enough action. Then it was about preventing impacts projected for the future. Now it’s about responding to the impacts we are seeing all around us in time to prevent them from getting completely out of hand. We have no more time to lose.
The IPCC report was prepared by 209 lead authors, 50 review editors and more than 600 contributing authors representing 39 countries. They assessed a staggering 54,677 comments from nearly 1,100 expert reviewers worldwide.
Few of these authors were involved in the 1990 assessment—some hadn’t graduated from college at the time. Authors came from all parts of the world and from all kinds of institutions: government, academic, and industry. Among the authors: A scientist from ExxonMobil. Past assessments have included authors from Chevron, Shell, Aramco and the Tokyo Electric Power Co., as well as noted climate change skeptics from around the world.
Put simply, there has never been a more comprehensive scientific review of global climate change, nor a more definitive agreement on a conservative estimate of what is happening to our world and what is causing it to change.
This science is settled, and the facts are clear. Climate change is the central environmental challenge of our time. We have an obligation to stand up and confront this widening scourge for the sake of future generations.
In the lead up to the release of the IPCC’s definitive assessment a handful of organizations and individuals, some with ties to the fossil fuel industry, have tried to make hay out of an apparent slowdown in the rate of global surface temperature increases in recent years. Don’t be misled, and don’t be distracted.
The IPCC report notes that over 90 percent of the extra heat trapped by carbon dioxide and other greenhouse gases goes into the oceans, and there is no evidence of any slowdown in that heat buildup. Equally important, the claimed slowdown in surface warming is (literally) statistically insignificant.
Natural variability and short term factors, such as volcanoes, always have and always will cause year-to-year variations in the climate. That means that the shorter the time period you look at, the larger the uncertainty in determining any trend, and the more sensitive the result to the starting point. Again, the IPCC report makes this clear: “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.”
Specifically, the uncertainty bounds on the 15-year trend starting in 1998 (the period of the claimed slowdown) range from -0.05 degrees per decade to +0.15 degrees per decade, which encompasses the central estimate of the warming trend since 1950 of 0.12 degrees per decade. That’s what statistically insignificant means. Moreover, if you look at a 15 year trend starting in 1995, rather than 1998, the trend estimate is +0.02 to +0.24 degrees per decade, which is FASTER than the overall trend since 1950.
The bottom line is that we are living in the warmest period since reliable global temperature measurements began in 1880. The report notes: "Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850." In other words, the last decade was the warmest on record, beating out the 1990s which previously held that distinction. The 1990s themselves became the hottest decade at the time by beating out the 1980s.
In fact, the impacts of climate change - including sea level rise, the melting of sea ice and glaciers and rising ocean acidity levels worldwide - have been accelerating.
Last year, for example, Arctic sea ice melted to its lowest level since we began measuring it with satellite images in 1978. This month marked the 6th-lowest level on record for this ice, which has been declining by about 12 percent each decade since the measurements began.
In the United States, we're already paying a heavy price for climate change. We suffered $140 billion in damages last year - the hottest year on record across the continental United States - from crop losses, wildfires and severe storms.
The federal government picked up the lion’s share of the tab, at a cost of $1,100, on average, per American taxpayer. These costs will continue to rise if climate-changing pollution is not abated.
In the coming days, the usual climate change deniers, some in the fossil fuel industry, and their allies on Capitol Hill, will trot out the same old bromides they’ve been parroting since the first IPCC report in 1990 to try to confuse the public and delay, even further, needed action to protect our children’s future.
The rest of us must stand on more solid ground.
We must stand on facts and data.
We must stand on what 97 percent of the world’s climate scientists are telling us, what we know to be true about our changing world, and what we’ve seen and experienced in our own backyards.
The science is settled. Now we must broaden the level of agreement on what to do about it.
We can reduce our carbon footprint – at home and abroad – by setting common-sense limits on the dangerous carbon pollution from our power plants.
We can reduce our reliance on fossil fuels by investing in efficiency, so that we can do more with less, and in wind, solar and other sources of clean and renewable power.
And we can stand up to this global environmental malady today, so that our children don’t inherit climate chaos tomorrow.
That is what the best science in the world tells us we must do – and that is also what we know is the right thing to do – to meet our most basic obligation to our children and future generations.
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