Today being Earth Day, I’ve been musing about the state of our environment and where we’re heading.

Forty-four years after the first Earth Day in 1970 (when I was a teenager and the Earth Day coordinator in my junior high school), a lot has been accomplished. Our skies are generally cleaner (in the U.S. at least). We’re no longer dumping raw sewage into our rivers, and fish have returned to many of our most polluted bodies of water -- including Ohio’s infamous Cuyahoga River, which caught fire several times in the 1960s. The most toxic pesticides, such as DDT, have been banned and bird species like the bald eagle and peregrine falcon have rebounded by near extinction from the Lower 48 states.

But all is not well. The looming crisis of climate change is ever more obvious today -- even as climate science deniers and the well-paid politicians they invest in create an impression in the media that there remains significant debate about global warming.

Climate change threatens the environmental gains we’ve realized since the 1970s with far greater environmental catastrophe over the coming decades and centuries. The IPCC (Intergovernmental Panel on Climate Change) has recently released its three-part Fifth Assessment Report -- the most definitive to date in describing what we can expect and what we are already experiencing with climate change.

Understanding IPCC

IPCC and its periodic reports can be pretty confusing, especially for acronym-challenged individuals like me, so let me provide a bit of background: IPCC was established by the United National Environment Program (UNEP) and the World Meteorological Organization (WMO) in 1988 to better understand climate change, what its impacts might be, and what to do about it.

The Panel released its first Assessment Report two years later, in 1990. Like the subsequent Assessment Reports, this was really three reports from three different Working Groups: Here’s how these Working Groups are described on the IPCC website:

-- Working Group I assesses the physical scientific aspects of the climate system and climate change.

-- Working Group II assesses the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change, and options for adapting to it. This group focuses both on sectors (water resources; ecosystems; food & forests; coastal systems; industry; human health) and regions (Africa; Asia; Australia & New Zealand; Europe; Latin America; North America; Polar Regions; Small Islands).

-- Working Group III assesses options for mitigating climate change through limiting or preventing greenhouse gas emissions and enhancing activities that remove them from the atmosphere.

An expanding series
of IPCC reports

Since the first Assessment Report in 1990, Supplemental Reports were published in 1992 by Working Groups I and II; the Second Assessment Report was published in 1995; the Third in 2001; the Fourth in 2007; and the Fifth Assessment Report was released in three phases starting last September.

With this Fifth Assessment Report, the sub-reports were released as follows: the Working Group I Report, "Climate Change 2013: The Physical Science Basis" (1,535 pages!), was released in September 2013 in Stockholm; the Working Group II Report, "Climate Change 2014: Impacts, Adaptation, and Vulnerability," was released in March 2014 in Yokohama, Japan; and the Working Group III Report, "Climate Change 2014: Mitigation of Climate Change," was released in April 2014 in Berlin. A Synthesis Report of the Firth Assessment Report will be published later this year.

In addition to these main reports, IPCC has published nine special reports over the years, including Renewable Energy Sources and Climate Change Mitigation (2011), Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (2011), and Carbon Dioxide Capture and Storage (2005).

IPCC reports as a
basis for policy

The ongoing IPCC reports have provided the foundation for important policies at an international level.

Starting in 1990, when the first IPCC Assessment Report was published, the UN General Assembly decided to initiate negotiations on how to regulate greenhouse gas emissions, and in 1992 the United Nations Framework Convention on Climate Change (UNFCCC) was opened for signatures at the UN Conference on Environment and Development in Rio de Janeiro, Brazil.

By 1996, IPCC had published comprehensive guidelines that countries could use in carrying out detailed greenhouse gas inventories, and these formed the basis of the UNFCCC Kyoto Protocol, which was adopted a year later and went into effect in 2005.

Ever-more-certain science,
but stalling policy action

Each subsequent IPCC Assessment Report, especially the most recent, has painted a clearer and more detailed picture of what is happening to the Earth’s climate and the human causes of those changes.

Unfortunately, where the early reports included a range of impacts we could expect, reality has demonstrated the high end of the range. In other words, the scientists in IPCC have been shown to be conservative in their projections of the severity and speed of climate change.

In the Working Group I report from the 5th Assessment Report, global mean temperatures by 2100 are now expected to be 3.7 to 4.8 degrees C (6.7 to 8.6 degrees F) higher than pre-industrial levels -- up significantly from the early Assessment Reports. Already an 0.61 degrees C (1.1 degrees F) increase in global temperature has been measured.

The Working Group II report concluded with "very high confidence" that "impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant vulnerability and exposure of some ecosystems and many human systems to current climate variability."

The impacts of climate-related extremes, according to this Working Group II report, will include "alteration of ecosystems, disruption of food production and water supply, damage to infrastructure and settlements, morbidity and mortality, and consequences for mental health and human well-being."

Next week I’ll speculate as to what it will take to bring about real action on climate change.

Alex Wilson is the founder of BuildingGreen, Inc. and the Resilient Design Institute (www.resilientdesign.org), both based in Brattleboro. Send comments or suggestions for future columns to alex@buildinggreen.com.