Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.Now, at COP23, the 5th Assessment Report (AR5) has now been out for 3 years and in this report, the language was a bit stronger:
Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems. Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia.Last Friday (03 November 2017), despite the climate change denial of the current administration in the White House and much uncertainty about whether the release would occur, 13 federal agencies unveiled the findings of the U.S. Global Change Research Program in Climate Science – the 4th National Climate Assessment Report (NCA4) The format of this report has many analogies to the IPCC report, but is focused on U.S. science and impacts. Here is their statement about what is happening:
Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.
Since NCA3, stronger evidence has emerged for continuing, rapid, human-caused warming of the global atmosphere and ocean. This report concludes that “it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”And in more detail:
The frequency and intensity of extreme heat and heavy precipitation events are increasing in most continental regions of the world (very high confidence). These trends are consistent with expected physical responses to a warming climate. Climate model studies are also consistent with these trends, although models tend to underestimate the observed trends, especially for the increase in extreme precipitation events (very high confidence for temperature, high confidence for extreme precipitation). The frequency and intensity of extreme high temperature events are virtually certain to increase in the future as global temperature increases (high confidence). Extreme precipitation events will very likely continue to increase in frequency and intensity throughout most of the world (high confidence).
- Annual average temperature over the contiguous United States has increased by 1.2°F (0.7°C) for the period 1986–2016 relative to 1901–1960 and by 1.8°F (1.0°C) based on a linear regression for the period 1895–2016 (very high confidence).
- Increases of about 2.5°F (1.4°C) are projected for the period 2021–2050 relative to 1976–2005 in all RCP scenarios, implying recent record-setting years may be “common” in the next few decades (high confidence).
A report from 13 federal agencies says extreme weather events have cost the United States $1.1 trillion since 1980.It wasn't clear as to whether the economic impact of this year's three hurricanes were factored into that price tag. But what is clear, is that each year and with each additional COP, the costs of loss and damage associated with the impacts of climate change are rising.
Science in reports such as those from the IPCC has driven action and policy development at the international level. In fact, the first report of the IPCC directly led to the creation of the U.N. Framework Convention on Climate Change and the reason we have COP meetings each year. As the evidence builds, words such as "urgency" and "ambition" are routinely heard around the halls here in Bonn, although negotiations are still slow in resulting in implementation of specific actions that would actually make a difference in this global challenge. The science was beginning to inform policy in the U.S. under the Obama Administration, but alas, exactly one year ago, at COP22, we watched the election results come in and new that things would change.
Again, from the NY Times article:
"This report has some very powerful, hard-hitting statements that are totally at odds with senior administration folks and at odds with their policies,” said Philip B. Duffy, president of the Woods Hole Research Center. “It begs the question, where are members of the administration getting their information from? They’re obviously not getting it from their own scientists.”Relatively little reaction came out of the White House last Friday except for one statement:
“The climate has changed and is always changing,” Raj Shah, a White House spokesman, said in the statement. “As the Climate Science Special Report states, the magnitude of future climate change depends significantly on ‘remaining uncertainty in the sensitivity of Earth’s climate’” to greenhouse gas emissions, he added.Note the careful insertion of the word "uncertainty" in this statement. So as scientists grow increasingly confident in terms of the impacts and causes of climate change, we have an administration in the U.S. that prefers to cast doubt; attempt to break international agreements; silence, and in some cases, replace scientists; and scrub websites (e.g. of the EPA) of references to climate change.
In stark contrast, here in Bonn, scientists, activists, and other non-state actors, were invited to an open dialog today with the Parties who are negotiating the details of how to implement the Paris Agreement. From country after country, we heard about examples of national climate teams and consultations where scientists and politicians come together with indigenous peoples, representatives from the business community, and other stakeholders to discuss climate policy and action. Such dialogs alone won't immediately "solve" climate change but having everyone in the same room having productive discussions about the way forward is a much better approach than silencing the scientists and ignoring the data.