Conscious Climate: Science Specifics

Many people are skeptical that anything humans do could impact the entire planet. Understandably so: a well-known dictum of science is that extraordinary claims require extraordinary evidence.

The resources on this page do more than illustrate multiple lines of evidence of current human-induced global climate change — they suggest that nature, in response to our prodding, could unleash feedbacks that would dwarf the original provocation.

Hence the urgent need for massive reductions in greenhouse-gas emissions, and a bolstering of natural sinks, before a point of no return is reached.

Global Temperatures

How do you take a planet’s temperature? Do one or two years of cooler statistics mean the fever has broken?

Are Temperatures Rising? (NSIDC, 2008)
Yes, the globe is warming (Climate Progress, 2008)
Uh, yes, it’s STILL warming (New Scientist, 2008)

These links provide an understanding of how earth’s temperature is studied and of the various factors that affect it, including solar output as well as regional phenomena, like El Niño and La Niña.

Hadley Temperature Analysis (UK)
UK Met Office
UK Met Office FAQ
GISS Surface Temperature Analysis (US)

Somewhat technical views of how the two main repositories of world-wide temperature data do their analyses; follow the links on these pages to dig as deep as you want into the raw data and processing codes. For an animation of 5-year-mean temperature anomalies (relative to the 1951-1980 average) for the years 1880-2007, click here.

Glaciers, Ice-Sheets and Sea Ice

Changes to the crysphere (basically, the frozen part of the Earth system) offer the most obvious and dramatic evidence that warming is global in scale . . .

The State of the Cryosphere
Melting In The Heat? (BBC,2007)
State of the Canadian Cryosphere

From the US National Snow and Ice Data Center, time-series data for Northern Hemisphere snow cover, mountain glacier fluctuations, sea ice extent and concentration, changes in ice shelves, global sea level and a snapshot of current permafrost conditions. And from the BBC, a good summary of the state of the entire cryosphere, from West and East Antarctica to Arctic Ice to Greenland to permafrost and temperate-zone glaciers.

Global Glacier Changes (WGMS, 2008)
Worldwide Glacier Retreat (RealClimate, 2005)
Glaciers, Ice-Sheets and Sea Level (USGS, 2000)
Global Glacier Recession (NSIDC, 2003)
Tropical Glaciers/Mt. Kilimanjaro (RealClimate 2005)

"I heard on the radio the other day that there are plenty of glaciers around the world that are growing . . ." These links should dispel any doubts as to whether or not the world’s glaciers are sending a consistent signal on climate change. The last reference, somewhat technical, addresses briefly a controversy provoked by Al Gore’s mention of Mt. Kilimanjaro in his documentary "An Inconvenient Truth."

Small Glaciers Lead Greenland Decay (NASA, 2008)
Antarctic Ice Loss Speeds Up (2008)
Greenland Melt Sets Record (2007)
Greenland Ice Loss Accelerating (2006)
Greenland Ice Loss Doubles In Decade (2006)
Greenland Ice Melt (2005)

The Antarctic and Greenland ice-sheets, with enough water to raise sea levels by tens of meters, are the focus of intense international study. These resources demonstrate that the weight of recent evidence points to increasingly rapid melting, with an overall net loss of ice at both poles (the surveys by the GRACE satellites are particularly compelling).

Latest Arctic Ice News (NSIDC)
Serreze Lecture On Arctic Changes, 2007
Ice-Sheet Models and Observations (RealClimate)
NASA Provides New Ice-Sheet Perspectives (2006)
Models Underestimate Arctic Sea-Ice Loss (2007)
Models Can’t Yet Predict Sea-Ice Loss (RealClimate)

In 2007, thousands of scientists from around the world began focusing their efforts on documenting and understanding current climate changes taking place in polar regions. Hopefully, one payoff will be a better understanding of ice-sheet dynamics, as present IPCC projections are woefully unable to accommodate the degree of ice-sheet decay being observed . . .

Attribution (Are Humans Responsible?)

As a prelude to our page on Consensus & Denial, here are two references on the evidence that we humans are indeed responsible for the changes described in the other resources on this page.

Climate Change Detection/Attribution (NOAA, 2000)
Causes of Global Climate Change (PEW, 2008)
A Review Of The Facts (2007)
Human Fingerprints (UCC, 2006)

Short descriptions of how climate models, paleoclimate studies and/or current data have been used to determine the relative roles of natural versus human drivers of current climate change.

It’s Not Just CO2 (RealClimate, 2006)

There's a fairly lengthy cast of suspects in the case of global warming. So why the emphasis on CO2?

Tying CO2 Increases To Humans (RealClimate, 2004)

The fingerprint of human involvement doesn't rely on paleo evidence or models alone . . .

Understanding & Attributing Climate Change (IPCC 2007)

From Working Group I (The Physical Science Basis), Chapter 9 of Climate Change 2007, the 4th report of the IPCC.

The Carbon Cycle

Human-induced climate change boils down to our having altered, through the burning of fossil fuels, the long-term cycling of carbon between a series of chemical and biological sources and sinks. In particular, we have broken into geological stores accumulated over millions of years and released them into the atmosphere in little more than two centuries.

The Carbon Cycle (wikipedia)
Natural Carbon Cycle (2008)
North American Carbon Budget 2007 (Summary)
Canada’s Forests: Sink or Source? (2007)
Missing Carbon Sink Found (2007)

Here are some resources on the overall cycling of carbon in nature (some of it over millions of years) and on how humans have altered the cycle through fossil-fuel combustion and deforestation.

Southern Ocean CO2 Sink In Decline (2007)
Growth In Atmospheric CO2 Accelerating (2007)

Atmospheric concentrations of CO2 are growing at an accelerating rate, due to faster economic growth, rising carbon intensity and a decline in natural sinks.

The Role Of The Oceans

Oceans cover 70% of Earth’s surface, and their ability to store - and transport - vast quanitities of heat make them the most massive piece of the climate jig-saw puzzle.

Earth’s Big Heat Bucket (NASA, 2006)
Earth’s Energy Imbalance Hiding In Oceans (2005)

If greenhouse gases are forcing the Earth to absorb more energy than it emits, why don't global surface temperature increases reflect the total excess energy?

The Ocean’s Carbon Balance (NASA, 2008)
How Much More CO2 Can Ocean Hold? (2008)
Southern Ocean CO2 Sink Filling Fast (2007)

From NASA, Woods Hole and the University of East Anglia, descriptions of the oceans’ role as a sink for CO2 pumped into the atmosphere, and warnings about the limits of that role (and about the effects of increasing acidification).

Ocean Acidification
Methane Hydrates In The Sea Floor
Methane Hydrates Risk Analysis (2006 PDF, 53 pp.)
The Future Oceans (2006 PDF, 123 pp.)

From the German Advisory Council On Global Change, discussions of ocean acidification caused by absorbed CO2, an appraisal of the nature of, and risks presented by, frozen methane deposits on the sea floor, and a comprehensive overview of the possible effects of climate change on the oceans.

Ancient Climates

How do scientists infer the state of Earth’s climate going back millions of years — and what can their findings tell us about current warming?

Last Time CO2 Was This High (UCLA, 2009)

“The last time carbon dioxide levels were apparently as high as they are today [15 million years ago] — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland . . .” (full PDF paper here.)

Paleoclimateology (NASA)

A multi-page summary, from NASA’s Earth Observatory web-site, of how scientists use a variety of physical clues — from cave rocks to ocean sediments to ice cores to tree rings — to build a picture of both ancient and future climates.

Climate Timeline (NOAA)

An interactive education resource exploring climate over varying time-scales going back 100,000 years or more; the site map illustrates the breadth of related information to which you can link.

Climate Proxies

A gateway site to basic and advanced information on the full range of physical and biological clues scientists use to infer past climate conditions.

Climate Models

The suggestion that the case for human-caused climate change - either present or future - rests largely with climate models is false. Nevertheless, as models become more and more powerful, they offer clearer insights into the causes of current global warming and the likelihood of possible future outcomes depending on what steps humanity takes to reign it in.

Introduction To Climate Models
Physics of Climate Modeling (GISS, 2007)
Modeling Climate (Yale U.)
Modeling Climate (NOAA)
Global Climate Models (wikipedia)

Combined with with studies of ancient climates and observations of current events, climate models are important tools for projecting current and historical trends into the future, as well as for teasing out the cause-effect relationships between natural vs. human forcings and observed data. These five links lead to introductory resources on model construction, uses and limitations.

Climate Model Complexity

A short description of how growth in computing power and available data has led to increased sophistication in climate models.

Climate Model FAQ I (RealClimate, 2008)
Climate Model FAQ II (RealClimate, 2008)

A fascinating (though somewhat technical) two-part FAQ describing how models are created, tested, tweaked and “verified”, describing both their legitimate uses and limitations.

Models’ Accuracy Questioned
Perhaps It’s the Data?
Model-Data Mismatch Resolved?

Climate models are tested by determining how well they can reproduce known data when run using known starting conditions from the past. Discrepancies between predicted and observed data prompt a search for the reasons . . .

The Threat Of Runaway Climate Change

The need to deal with climate change NOW derives from two factors: the inertia of the climate system itself (which means that we could become committed to dangerous change many decades before its worst effects become apparent) and a growing awareness - based on studies of ancient climates - of the dominant role of natural feedbacks (which may kick in as earth’s temperature passes critical tipping points, reinforcing and accelerating subsequent climate change far beyond humanity’s ability to respond).

Non-Linear Climate Change (14 pp. PDF)
Inevitable Surprises (PNAS PDF, 2004)
Dangerous Climate Change (Hadley PDF, 2005)
Dangerous Climate Change (Stanford PDF, 2006)

Non-Linear Climate Change

A Paleo Perspective (NOAA 2008)
Antarctic Ice Cores Warn of Greater Warming

Warnings From The Past

Implications of an Arctic Meltdown (2009)
Will Feedbacks Amplify Global Warming? (2006)
Water Vapor Could Double Effect of CO2 (2008)
Key Amplifying Feedbacks (ClimateProgress, 2008)

Climate Feedbacks

Future Greenland Melt Underestimated? (2008)
Scientific Reticence & Sea-Level Rise (Hansen, 2007)

Greenland and Antarctic Ice Sheets

Permafrost Holds Vast Carbon Pool (2008)
Risk of Permafrost Thaw (UNEP, 2008)
Permafrost Vulnerability (2008)
Peat As Scary As Permafrost (2008)
Future of Canadian Permafrost

Permafrost and Clathrates

Potential Tipping Elements (Potsdam Institute, 2008)
Tipping Points In The Earth System (UK, 2007)
Tipping Points Near (Hansen PDF, 2008)
Tipping-Point video (Hansen 2008)
Urgency of Climate Change video (Hansen, 2008)
Climate Catastrophe (Hansen PDF, 2007)
Avoiding Catastrophe (Australian PDF, 2008)

Tipping-Points