The complete guide to modern day climate change

All the data you need to show that the world is warming

 

According to the IPCC 4th Assessment Report (2007):

• Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.
• At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.
• Paleoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years. The last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to 4 to 6 metres of sea level rise.
• Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the [Third Assessment Report's 2001]conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.

Let us take a look at some of the evidence:

This post is by guest Blogger Scott A. Mandia, Professor of Physical Sciences at Suffolk County Community College, Long Island, NY.  Mandia holds an M.S. Meteorology from Penn State University and a B.S. Meteorology from University of Lowell (now called UMass – Lowell). Mandia has been teaching introductory meteorology and paleoclimatology courses for 23 years.

Temperature Trends

20 of the warmest years on record have occurred in the past 25 years. The warmest year globally was 2005 with the years 2009, 2007, 2006, 2003, 2002, and 1998 all tied for 2^ndwithin statistical certainty. (Hansen et al., 2010) The warmest decade has been the 2000s, and each of the past three decades has been warmer than the decade before and each set records at their end. The odds of this being a natural occurrence are estimated to be one in a billion! (Schmidt and Wolfe, 2009)

According to NOAA climate monitoring chief Deke Arndt (Romm, 2009):

The last 10 years are the warmest 10-year period of the modern record. Even if you analyze the trend during that 10 years, the trend is actually positive, which means warming.

Figure 7.1 (IPCC, 2007) shows the global mean temperature anomalies (compared to 1961-1990) from the years 1850 to 2005. Figure 7.1a (NCDC, 2008) shows the global mean temperature anomalies with error bars from the years 1880 to 2007.

Figure 7.1: Global mean temperature anomalies (compared to 1961-1990) from the years 1850 to 2005

Figure 7.1a: Global mean temperature anomalies from the years 1880 to 2008

Figure 7.2 (Tamino, 2009) clearly shows that surface temperatures north of latitude 60^o are warming at an accelerated rate in the past few decades. Tamino retrieved 113 station records at latitude 60^oN or higher with at least 30 years of data.

Figure 7.2: Arctic surface temperatures since 1948.

Tamino (2009) explains here and here. The analyses show:

1. The Arctic has experienced a sudden, recent warming.
2. In the last decade extreme northern temperature has risen to unprecedented heights.
3. Over the last 3 decades, every individual station north of 70^o indicates warming, 13 of 17 are significant at 95% confidence, all estimated trend rates are faster than the global average, some are more than five times as fast.
4. Oft-repeated claims that “it was warmer in the 1930s” or “it was warmer in the 1940s” are wrong.
5. The idea that present arctic temperatures are about equal to their 1958 values is wrong.

Kauffman et al. (2009) also shows that the Arctic was experiencing long-term cooling in the past 2000 years according to Milankovitch cycles until very recently. Figure 7.3 (ibid) reveals this trend shift:

A Hockey Stick in Melting Ice

Figure 7.3: Recent warming reverses long-term arctic cooling

Kaufmann et al. summarizes their study:

The temperature history of the first millennium C.E. is sparsely documented, especially in the Arctic. We present a synthesis of decadally resolved proxy temperature records from poleward of 60 ^oN covering the past 2000 years, which indicates that a pervasive cooling in progress 2000 years ago continued through the Middle Ages and into the Little Ice Age. A 2000-year transient climate simulation with the Community Climate System Model shows the same temperature sensitivity to changes in insolation as does our proxy reconstruction, supporting the inference that this long-term trend was caused by the steady orbitally driven reduction in summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-long reconstruction occurring between 1950 and 2000.

Arctic Ice & Glacial Trends:

Further signs of this warming trend can be seen in the Northern Hemisphere Sea Ice Extent from the National Snow and Ice Data Center. Figure 7.4 shows sea ice extent since 1953. For January 1953 through December 1979, data have been obtained from the UK Hadley Centre and are based on operational ice charts and other sources. For January 1979 through July 2009, data are derived from satellite. Figure 7.4a shows the most current sea ice extent from satellite measurements. Sea ice extent has been dramatically reduced since 1953.

Figure 7.4: Northern Hemisphere sea ice extent since 1953

Figure 7.4a: Current Northern Hemisphere sea ice extent from satellite measurements

Sea ice extent is just part of the picture. Sea ice thickness has also been measured by submarine and ICESat satellite measurement.

Figure 7.5 (Rothrock, et al., 1999) shows sea ice thickness has substantially declined. Using data from submarine cruises, Rothrock and collaborators determined that the mean ice draft at the end of the melt season in the Arctic has decreased by about 1.3 meters between the 1950s and the 1990s.

Figure 7.5: Mean sea ice draft: Decrease in Arctic sea ice draft for 1958 to 1997.

Since 2004 and there has been a dramatic decrease in thickness according to NASA’s press release, NASA Satellite Reveals Dramatic Arctic Ice Thinning dated July, 2009. Some excerpts:

Using ICESat measurements, scientists found that overall Arctic sea ice thinned about 0.17 meters (7 inches) a year, for a total of 0.68 meters (2.2 feet) over four winters. The total area covered by the thicker, older “multi-year” ice that has survived one or more summers shrank by 42 percent. In recent years, the amount of ice replaced in the winter has not been sufficient to offset summer ice losses. The result is more open water in summer, which then absorbs more heat, warming the ocean and further melting the ice. Between 2004 and 2008, multi-year ice cover shrank 1.54 million square kilometers (595,000 square miles) — nearly the size of Alaska’s land area. During the study period, the relative contributions of the two ice types to the total volume of the Arctic’s ice cover were reversed. In 2003, 62 percent of the Arctic’s total ice volume was stored in multi-year ice, with 38 percent stored in first-year seasonal ice. By 2008, 68 percent of the total ice volume was first-year ice, with 32 percent multi-year ice.

Figure 7.5a (NASA, 2009) shows that overall ice thickness and multi-year ice (MY) thickness are decreasing.

Figure 7.5a: Northern Hemisphere sea ice thickness

Figure 7.5b: Northern Hemisphere sea ice thickness submarine & ICESAT combined

Figure 7.5b (Kwock & Rothrock, 2009) shows the mean thicknesses of six Arctic regions for the three periods (1958– 1976, 1993–1997, 2003–2007). Thicknesses have been seasonally adjusted to September 15. According to the authors:

“The overall mean winter thickness of 3.64 m in 1980 can be compared to a 1.89 m mean during the last winter of the ICESat record—an astonishing decrease of 1.75 m in thickness. Between 1975 and 2000, the steepest rate of decrease is 0.08 m/yr in 1990 compared to a slightly higher winter/summer rate of 0.10/0.20 m/yr in the five-year ICESat record (2003–2008). Prior to 1997, ice extent in the DRA was >90% during the summer minimum. This can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to <55% during the record setting minimum in 2007. This combined analysis shows a long-term trend of sea ice thinning over submarine and ICESat records that span five decades.“

	Peter Sinclair’s Climate Crock of the Week: 2009 Sea Ice Update Watch this video to learn about the 2009 Arctic sea ice measurements.
	Peter Sinclair’s Climate Crock of the Week: Ice Area vs. Volume Watch this video to learn about the difference between ice area and ice volume and why volume is more critical.

Velicogna (2009) used measurements from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass-loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009. During this time period the mass loss of the ice sheets were accelerating with time implying that the ice sheets contribution to sea level becomes larger with time. In Greenland (Fig. 7.6), the mass loss increased from 137 Gt/yr in 2002–2003 to 286 Gt/yr in 2007–2009. In Antarctica (Fig. 7.7) the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009.

Figure 7.6: Greenland Ice Mass Loss

Figure 7.7: Antarctic Ice Mass Loss

John Cook at Skeptical Science has several very good summaries of this research. See: An overview of Antarctic ice trends, An overview of Greenland ice trends, and Why is Greenland’s ice loss accelerating?.

Glaciers also are used as a signature for climate change. Summer melting, called ablation, controls the mass and extent of glaciers. According to the World Glacier Monitoring Service (2009), preliminary mass balance values for the observation periods 2005/06 and 2006/07 have been reported from more than 100 and 80 glaciers worldwide, respectively. The mass balance data are calculated based on all reported values as well as on the data from the 30 reference glaciers in nine mountain ranges in North America and Europe with continuous observation series back to 1980.

The average mass balance of the glaciers with available long-term observation series around the world continues to decrease, with tentative figures indicating a further thickness reduction of 1.3 and 0.7 metres water equivalent (m w.e.) during the hydrological years 2006 and 2007, respectively. The new data continues the global trend in accelerated ice loss over the past few decades and brings the cumulative average thickness loss of the reference glaciers since 1980 at almost 11.3 m w.e. (see Figures 7.8 and 7.9).

Figure 7.8: Mean annual specific mass balance of reference glaciers

Figure 7.9: Mean cumulative specific mass balance of all reported glaciers (black line) and the reference glaciers (red line)

Glacial extent is also being monitored. Figure 7.10 (ibid) shows worldwide glacial extent measurements with red being a decrease and blue being an increase in the length of the glacier.

Figure 7.10: Glacial extent – retreating (red) and advancing (blue)

In 2005 there were 442 glaciers examined, 26 advancing, 18 stationary and 398 retreating. 90% of worldwide glaciers are retreating. In 2005, for the first time ever, no observed Swiss glaciers advanced. Of the 26 advancing glaciers, 15 were in New Zealand. Overall there has been a substantial volume loss of 11% of New Zealand glaciers from 1975-2005, but the number of advancing glacier is still significant. (ibid)

Ocean Heat Content:

Much of the heat that is delivered by the sun is stored in the Earth’s oceans while only a fraction of this heat is stored in the atmosphere. Therefore, a change in the heat stored in the ocean is a better indicator of climate change than changes in atmospheric heat. Figures 7.11 and 7.12 (Richardson et al., 2009) and 7.13 (NODC, 2009) clearly show that the oceans have warmed significantly in recent years and the trend is 50% greater than that reported by the IPCC in 2007.

Figure 7.11: Change in energy content in different components of the earth system for two periods: 1961-2003 (blue bars) and 1993-2003 (pink bars).

Figure 7.12: Change in ocean heat content since 1951.

Figure 7.13: Change in ocean heat content since 1955.

There have been a few published articles by Loehle (2009), Pielke (2008), and Willis (2008) that suggest ocean heat content trend since 2003 has either been flat or slightly negative. Of course, a few years does not a trend make but these results appear to be in conflict with the current upward trend. von Shuckmann, Gaillard, and Le Traon (2009) address this apparent conflict in their article Global hydrographic variability patterns during 2003–2008. Their data extends to 2000 m of ocean depth in contrast to Loehle (2009), Pielke (2008), and Willis (2008) data that only extends to 700 m. von Shuckmann, Gaillard, and Le Traon (2009) show that the heat content of the upper 500 m of ocean are subject to strong seasonal and interannual variations primarily due to salinity changes. However, when considering the heat content of the upper 2000 m of ocean, global mean heat content and height changes are clearly associated with a positive trend during the 6 years of measurements. Figure 7.14 below shows this trend.

Figure 7.14: Change in global heat content for the uppermost 2000 m of ocean between 2003 and 2008

Murphy et al. (2009) examined the Earth’s energy balance since 1950 including ocean heat content, radiative forcing by long-lived trace gases, and radiative forcing from volcanic eruptions. They considered the emission of energy by a warming Earth by using correlations between surface temperature and satellite data and show that the heat gained since 1950 is already quite significant. Their findings are illustrated below. (Cook, 2009)

Figure 7.15: Total Earth Heat Content from 1950 (ibid)

The oceans are taking in almost all of the excess heat since the 1970s which underscores the point that ocean heat content is a better indicator of global warming than atmospheric temperatures. Much of this ocean heat will be vented to the atmosphere in the future thus accelerating global warming.

A superb discussion on this topic can be found at Skeptical Science’s How we know global warming is still happening.

Precipitation Trends:

Figure 7.16 (IPCC, 2007) shows the Palmer Drought Severity Index (PDSI). The PDSI is a prominent index of drought. Red and orange areas are drier (-PDSI) than average and blue and green areas are wetter (+PDSI) than average. The smooth black curve shows decadal variations. The PDSI curve reveals widespread increasing African drought, especially in the Sahel. Note also the wetter areas, especially in eastern North and South America and northern Eurasia.

Figure 7.16: Palmer Drought Severity Index (PDSI)

Zhang et al. (2007), IPCC (2007), and Held and Soden (2006) conclude that global warming due to human activities is increasing the severity of drought in areas that already have drought and causing more rainfall in areas that are already wet.

Zhang et al. (2007) considered three groups of global climate model simulations and compared those simulations to the observed precipitation between 70^o north and 40^o south as shown in Figure 7.17 below.

• ANT denoted simulations included estimates of historical ANThropogenic (human) forcing only which included greenhouse gases and sulfate aerosols.
• NAT4 denoted simulations included just NATural external forcings only.
• ALL denoted simulations include BOTH of the above – natural and human forcing.

Figure 7.17: Observed precipitation vs. various simulations

This clearly shows that the ALL simulations (a and d) do a much better job of matching observed precipitation trends than either ANT (b and e) or NAT (c and f) alone. In fact, the correlations: ALL = 0.83, ANT = 0.69 and NAT4 = 0.02. It is for this reason that Zhang et al. (2007) conclude that changes in precipitation trends cannot be explained by natural forcing only and it certainly parallels what the IPCC WGI and WGII reports suggest.

Figure 7.18: Changes in observed vs. simulated precipitation anomalies (ibid)

Figure 7.18 shows that the models do not predict the mid-latitude trends at all. Regional precipitation pattern predictions are NOT a strong suit of the models which modelers have stated. What this image does show however, is that areas of green and yellow show where the model trends match those of the observed trends and the models do a decent job of forecasting the correct trends in most regions.

U.S. Climate Extremes Index (CEI):

The U.S. CEI is the arithmetic average of the following five or six# indicators of the percentage of the conterminous U.S. area:

1. The sum of (a) percentage of the United States with maximum temperatures much below normal and (b) percentage of the United States with maximum temperatures much above normal.
2. The sum of (a) percentage of the United States with minimum temperatures much below normal and (b) percentage of the United States with minimum temperatures much above normal.
3. The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the PDSI and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.
4. Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.
5. The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.
6. * The sum of squares of U.S. landfalling tropical storm and hurricane wind velocities scaled to the mean of the first five indicators.

# The sixth indicator is experimental and is included in the experimental version of the CEI.
* The sixth indicator is only utilized when the period of interest includes months with significant tropical activity. For practical purposes, the CEI does not include the sixth indicator for the cold season (Oct-Mar), winter (Dec-Feb) or spring (Mar-May). It also cannot be calculated independent of the first five indicators. (Gleason, 2009)

Figure 7.19 (ibid) shows that in the United States, extremes in climate are on the increase since 1970.

Figure 7.19: United States Climate Extremes Index

Are These Trends Unusual?:

They are unprecedented in the modern record!

• The concentration of CO₂ has reached a record high relative to the past 15 million years and has done so at an exceptionally fast rate.
• Most of the warming in the past 50 years is attributable to human activities.
• CO₂ concentrations are known accurately for the past 650,000 years. During that time, they varied between 180 ppm and 300 ppm. As of March 2009 CO₂ is 385 ppm which took about 100 years to increase. For comparison, it took over 5,000 years for an 80 ppm rise after the last ice age.
• Higher values than today have only occurred over many millions of years.
• The last time CO₂ levels were this high, sea level was 25 to 40 meters higher than present day.
• Although large climate changes have occurred in the past, there is no evidence that they took place at a faster rate than the present warming.
• If projections of a 5 ^oC warming in this century are realized, Earth will have experienced the same amount of global warming as it did at the end of the last glacial maximum.
• There is no evidence that this rate is matched to a comparable global temperature increase over the last 50 million years!

Sea-Level Rise:

Sea-level rise due to global warming is a serious threat, especially to coastal communities in developing countries. Sea level gradually rose in the 20th century and is currently rising at an increased rate, after a period of little change between AD 0 and AD 1900. Sea level is predicted to rise at an even greater rate in this century, with 20th century estimates of 1.7 mm per year (IPCC, 2007). When climate warms, ice on land melts and flows back into the oceans raising sea levels. Also, when the oceans warm, the water expands (thermal expansion) which raises sea levels. Figure 7.20 (IPCC, 2007) shows the projected sea-level rise through AD 2100.

Figure 7.20: Projected sea-level rise through AD 2100

Figure 7.21 (Richardson et al., 2009) shows that IPCC 1990 projected sea level increases were too conservative. The latest observations show that sea levels have risen faster than previous projections.

Figure 7.21: Observed sea-level rise between 1970 and 2008 compared to IPCC projections

Figure 7.21a (Colorado Center for Astrodynamics Research) shows the current sea level change data using seasonally adjusted values from TOPEX and Jason.

Figure 7.21a: Current measured sea level change

Mazria & Kirshner (2005) in Nation Under Siege: Sea Level Rise at Our Doorstep, a coastal impact study, show that beginning with just one meter of sea level rise, US cities would be physically under siege, with calamitous and destabilizing consequences. One can view the impact of sea level rise of various US cities at their interactive Website.

Lemonick (2010) writes in the article The Secret of Sea Level Rise: It Will Vary Greatly by Region:

As the world warms, sea levels could easily rise three to six feet this century. But increases will vary widely by region, with prevailing winds, powerful ocean currents, and even the gravitational pull of the polar ice sheets determining whether some coastal areas will be inundated while others stay dry.

Climate Change and Hurricanes:

A recent paper published by some of the top hurricane researchers in the field (Knutson, et al. 2010) concludes:

…future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre.

According to a review of the most recent literature, Vechi, Swanson, and Soden (2008) conclude that predicting the future of hurricane activity is at a crossroads. Vechi et al. compared the observed relation of the power dissipation index (PDI) vs. sea-surface temperatures (SST) in the main development region of Atlantic hurricanes. (PDI is the cube of the instantaneous tropical cyclone wind speed integrated over the life of all storms in a given season; more intense and frequent basinwide hurricane activity lead to higher PDI values.) There are two very different futures depending on whether absolute SST or relative SST controls PDI.

Figure 7.22 (ibid) shows PDI anomalies based on absolute SST.

Figure 7.22: PDI anomalies based on absolute SST

By 2100, the lower end of the model projections shows a PDI comparable to that of 2005, when four major hurricanes (sustained winds of over 100 knots) struck the continental United States, causing more than $100 billion in damage. The upper end of the projections exceeds 2005 levels by more than a factor of two. Combined with rising sea levels, coastal communities face a bleak future if absolute SST determines hurricane activity and strength.

Figure 7.23 (ibid) shows PDI anomalies based on “relative SST” which is the SST in the tropical Atlantic main development region relative to the tropical mean SST.

Figure 7.23: PDI anomalies based on relative SST

A future where relative SST controls Atlantic hurricane activity is a future similar to the recent past, with periods of higher and lower hurricane activity relative to present-day conditions due to natural climate variability, but with little long-term trend. Even in this scenario, rising sea levels will still allow hurricanes to do more damage in the future than in present day.

Because the correlation of PDI vs. absolute SST and PDI vs. relative SST are equivalent, Vechi et al. conclude that more research is needed in this area.

IGBP Climate-Change Index:

Figure 7.24: IGBP Climate-Change Index (Click for larger image)

The IGBP Climate-Change Index brings together key indicators of global change: atmospheric carbon dioxide, temperature, sea level and sea ice. It will be released annually. The index gives an annual snapshot of how the planet’s complex systems – the ice, the oceans, the land surface and the atmosphere – are responding to the changing climate. The index rises steadily from 1980 – the earliest date the index has been calculated. The change is unequivocal, it is global, and it is in one direction – up!

Each parameter is normalized between -100 and +100. Zero is no annual change. One hundred is the maximum-recorded annual change since 1980. The normalised parameters are averaged. This gives the index for the year. The value for each year is added to that of the previous year to show the cumulative effect of annual change. (IGBP Climate-Change Index, 2010)

With all of this evidence for global warming, it is quite difficult to understand why some people still claim that there is no global warming, or more absurdly, that the climate is currently cooling.

For complete source information please see Works Cited.

Mandia offers more climate change information at the links below:
Global Warming: Man or Myth?
Global Warming Blog
“Global Warming Fact of the Day” Facebook Group

 

From Climate Progress

Expert credibility in climate change

1.            William R. L. Anderegg ^a , ¹ , James W. Prall ^b

2.     

3.            Jacob Harold ^c , and   Stephen H. Schneider ^a , ^d , ¹

4.                             

+Author Affiliations

1.                  ^aDepartment of Biology, Stanford University, Stanford, CA 94305;

2.                  ^bElectrical and Computer Engineering, University of Toronto, Toronto, ON, Canada M5S 3G4;

3.                  ^c William and Flora Hewlett Foundation, Palo Alto, CA 94025; and

4.                  ^dWoods Institute for the Environment, Stanford University, Stanford, CA 94305

1.                                Contributed by Stephen H. Schneider, April 9, 2010 (sent for review December 22, 2009)

Abstract

Although preliminary estimates from published literature and expert surveys suggest striking agreement among climate scientists on the tenets of anthropogenic climate change (ACC), the American public expresses substantial doubt about both the anthropogenic cause and the level of scientific agreement underpinning ACC. A broad analysis of the climate scientist community itself, the distribution of credibility of dissenting researchers relative to agreeing researchers, and the level of agreement among top climate experts has not been conducted and would inform future ACC discussions. Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.

·       Original link see here 

The Discovery of Global Warming

A thorough history of our understanding (and misunderstanding) of how atmospheric CO2 affects climate can be found at this site by the American Institute of Physics. ↩

Planetary Desolation

… please remember what the nation’s top climate scientist has said:

… the most serious effects will be visited upon the young and the unborn, the generations that bear no responsibility for the problem.

The most important effects, I believe, will be those that are irreversible for all practical purposes, specifically (1) extermination of species, and (2) ice sheet disintegration and sea level rise. If we continue business-as-usual energy policy, using more and more fossil fuels, it is likely that we will have:  (1) rapid climate change that will combine with other pressures on species to cause the rate of extinction of plants and animals to increase markedly, leading in some cases to ecosystem collapse, snowballing extinctions, and a more desolate planet for future generations.  (2) meter-scale sea level rise this century, and ice sheets in a state of disintegration that guarantees future sea level rise in the 10-meter-scale, with a continual reworking of future global coastlines out of humanity’s control.

I would add that the planetary desolation our continued inaction would leave our children includes the loss of the inland glaciers that provide fresh water for a billion people, irreversible ocean acidification and Dust-Bowlification across much of the habited land mass (see “Hell and High Water “).
Back when I wrote my 2006 book, it took a lot of effort interviewing top climate scientists and finding relevant studies to figure out what will happen in the world of tripled or quadrupled CO2 concentrations (from preindustrial levels) we are heading toward on our current emissions path.  Scientists hadn’t been doing a lot of analysis of those ’scary’ scenarios because they had assumedHomo ’sapiens’ sapiens would not be so stupid as to ignore their science-based warnings.
Now that the scientific community knows better, we’re seeing more and more studies of the impact of a tripling (825 ppm) or quadrupling (1100 ppm) — which is not to say that a doubling (to 550 ppm) wouldn’t be catastrophic:

• Science: CO2 levels haven’t been this high for 15 million years, when it was 5° to 10°F warmer and seas were 75 to 120 feet higher — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm.”
• New study of Greenland under “more realistic forcings” concludes “collapse of the ice-sheet was found to occur between 400 and 560 ppm” of CO2

It’s just that a tripling or quadrupling leads to impacts that are as far beyond catastrophic as those catastrophic impacts are beyond our current climate.  Here’s just a few analyses from the last two years:

• U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm.
• Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year — and that isn’t the worst case, it’s business as usual!”
• New study puts the ‘hell’ in Hell and High Water:  Must-read NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path
• Climate change expected to sharply increase Western wildfire burn area — as much as 175% by the 2050
• Ocean dead zones to expand, “remain for thousands of years”
• Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100
• Science: CO2 levels haven’t been this high for 15 million years, when it was 5° to 10°F warmer and seas were 75 to 120 feet higher — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm.”
• Nature Geoscience study: Oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred
• Half of world’s population could face climate-driven food crisis by 2100

And that isn’t the worst case.  No, the worst case is that the temperature rise occurs in 50 years, not 90 — and that the impacts last for centuries:

• UK Met Office: Catastrophic climate change, 13-18°F over most of U.S. and 27°F in the Arctic, could happen in 50 years, but “we do have time to stop it if we cut greenhouse gas emissions soon.”
• NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe

This is the “plausible worst case scenario” for 2060 from the UK Met Office that occurs in 10% of model runs of high emissions with the carbon cycle feedbacks [temperature in degrees Celsius, multiple by 1.8 for Fahrenheit]:

Of course, the above temperature plot is just for a mean global warming 5.4°C (9.7°F), which is business as usual for 2100 according to many analyses (see M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20° F).
But what’s really scary is that:

1. All of those beyond catastrophic impacts would be happening simultaneously, making it all but impossible to imagine that the devastated rich countries would be able to offer much assistance to the beyond-devastated poorer countries.
2. We’re doing this to our children in spite of being warned (see Is the global economy a Ponzi scheme?) — in spite of being told by virtually every major economic analysis that it could be avoided at a net cost of 1/10 of a penny on the dollar, not counting all of the ancillary benefits (improved public health, sharp drop in money flowing overseas to buy oil).

Post  from climate progress                          

Global Climate Change Indicators

National Oceanic and Atmospheric Administration

National Climatic Data Center

Many lines of scientific evidence show the Earth's climate is changing. This page presents the latest information from several independent measures of observed climate change that illustrate an overwhelmingly compelling story of a planet that is undergoing global warming. It is worth noting that increasing global temperature is only one element of observed global climate change. Precipitation patterns are also changing; storms and other extremes are changing as well.

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How do we know the Earth's climate is warming?

Thousands of land and ocean temperature measurements are recorded each day around the globe. This includes measurements from climate reference stations, weather stations, ships, buoys and autonomous gliders in the oceans. These surface measurements are also supplemented with satellite measurements. These measurements are processed, examined for random and systematic errors, and then finally combined to produce a time series of global average temperature change. A number of agencies around the world have produced datasets of global-scale changes in surface temperature using different techniques to process the data and remove measurement errors that could lead to false interpretations of temperature trends. The warming trend that is apparent in all of the independent methods of calculating global temperature change is also confirmed by other independent observations, such as the melting of mountain glaciers on every continent, reductions in the extent of snow cover, earlier blooming of plants in spring, a shorter ice season on lakes and rivers, ocean heat content, reduced arctic sea ice, and rising sea levels.

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The Global Surface Temperature is Rising

Global annual average temperature measured over land and oceans. Red bars indicate temperatures above and blue bars indicate temperatures below the 1901-2000 average temperature. The black line shows atmospheric carbon dioxide concentration in parts per million.

Global average temperature is one of the most-cited indicators of global climate change, and shows an increase of approximately 1.4°F since the early 20^thCentury. The global surface temperature is based on air temperature data over land and sea-surface temperatures observed from ships, buoys and satellites. There is a clear long-term global warming trend, while each individual year does not always show a temperature increase relative to the previous year, and some years show greater changes than others. These year-to-year fluctuations in temperature are due to natural processes, such as the effects of El Ninos, La Ninas, and the eruption of large volcanoes. Notably, the 20 warmest years have all occurred since 1981, and the 10 warmest have all occurred in the past 12 years.

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U.S. Surface Temperature is also Rising

Annual surface temperatures for the contiguous U.S. compared to the 20^th Century (1901-2000) average. Calculated from the U.S. Historical Climatology Network (USHCN version 2). More information: U.S. Surface Temperature Data, USHCN v2.

Surface temperatures averaged across the U.S. have also risen. While the U.S. temperature makes up only part of the global temperature, the rise over a large area is not inconsistent with expectations in a warming planet. Because the U.S. is just a fraction of the planet, it is subject to more year-to-year variability than the planet as a whole. This is evident in the U.S. temperature trace.

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Sea Level is Rising

Annual averages of global sea level. Red: sea-level since 1870; Blue: tide gauge data; Black: based on satellite observations. The inset shows global mean sea level rise since 1993 - a period over which sea level rise has accelerated. More information: Coastal Sensitivity to Sea Level Rise (USGCRP) and Climate Change 2007: The Physical Science Basis.

Global mean sea level has been rising at an average rate of approximately 1.7 mm/year over the past 100 years (measured from tide gauge observations), which is significantly larger than the rate averaged over the last several thousand years. Since 1993, global sea level has risen at an accelerating rate of around 3.5 mm/year. Much of the sea level rise to date is a result of increasing heat of the ocean causing it to expand. It is expected that melting land ice (e.g. from Greenland and mountain glaciers) will play a more significant role in contributing to future sea level rise.

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Global Upper Ocean Heat Content is Rising

Time series of seasonal (red dots) and annual average (black line) of global upper ocean heat content for the 0-700m layer since 1955. More information:BAMS State of the Climate in 2009.

While ocean heat content varies significantly from place to place and from year-to-year (as a result of changing ocean currents and natural variability), there is a strong trend during the period of reliable measurements. Increasing heat content in the ocean is also consistent with sea level rise, which is occurring mostly as a result of thermal expansion of the ocean water as it warms.

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Northern Hemisphere Snow Cover is Retreating

Average of monthly snow cover extent anomalies over Northern Hemisphere lands (including Greenland) since Nov 1966. Right: Seasonal snow cover extent over Northern Hemisphere lands since winter 1966-67. Calculated from NOAA snow maps. From BAMSState of the Climate in 2009 report.

Northern Hemisphere average annual snow cover has declined in recent decades. This pattern is consistent with warmer global temperatures. Some of the largest declines have been observed in the spring and summer months.

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Glacier Volume is Shrinking

Cumulative decline (in cubic miles) in glacier ice worldwide. More information: Global Climate Change Impacts in the U.S.

Warming temperatures lead to the melting of glaciers and ice sheets. The total volume of glaciers on Earth is declining sharply. Glaciers have been retreating worldwide for at least the last century; the rate of retreat has increased in the past decade. Only a few glaciers are actually advancing (in locations that were well below freezing, and where increased precipitation has outpaced melting). The progressive disappearance of glaciers has implications not only for a rising global sea level, but also for water supplies in certain regions of Asia and South America.

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U.S. Climate Extremes are Increasing

Enlarge above graph. Annual Climate Extremes Index (CEI) value for the contiguous United States. Larger numbers indicate more acive climate extremes for a year. More information: CEI.

One way climate changes can be assessed is by measuring the frequency of events considered "extreme" (among the most rare of temperature, precipitation and storm intensity values). TheClimate Extremes Index (CEI) value for the contiguous United States is an objective way to determine whether extreme events are on the rise. The figure to the left shows the the number of extreme climate events (those which place among the most unusual of the historical record) has been rising over the last four decades.

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How do we know humans are the primary cause of the warming?

A large body of evidence supports the conclusion that human activity is the primary driver of recent warming. This evidence has accumulated over several decades, and from hundreds of studies. The first line of evidence is our basic physical understanding of how greenhouse gases trap heat, how the climate system responds to increases in greenhouse gases, and how other human and natural factors influence climate. The second line of evidence is from indirect estimates of climate changes over the last 1,000 to 2,000 years. These estimates are often obtained from living things and their remains (like tree rings and corals) which provide a natural archive of climate variations. These indicators show that the recent temperature rise is clearly unusual in at least the last 1,000 years. The third line of evidence is based on comparisons of actual climate with computer models of how we expect climate to behave under certain human influences. For example, when climate models are run with historical increases in greenhouse gases, they show gradual warming of the Earth and ocean surface, increases in ocean heat content, a rise in global sea level, and general retreat of sea ice and snow cover. These and other aspects of modeled climate change are in agreement with observations.

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Climate Model Indications and the Observed Climate

Simulated global temperature in experiments that include human influences (pink line), and model experiments that included only natural factors (blue line). The black line is observed temperature change.

Global climate models clearly show the effect of human-induced changes on global temperatures. The blue band shows how global temperatures would have changed due to natural forces only (without human influence). The pink band shows model projections of the effects of human and natural forces combined. The black line shows actual observed global average temperatures. The close match between the black line and the pink band indicates that observed warming over the last half-century cannot be explained by natural factors alone, and is instead caused primarily by human factors.

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800,000 Year Record of Carbon Dioxide (CO₂) Concentrations

Carbon dioxide concentration (parts per million) for the last 800,000 years, measured from trapped bubbles of air in an Antarctic ice core. More information: Climate Change Impacts on the U.S.

Over the last 800,000 years, natural factors have caused the atmospheric carbon dioxide (CO₂) concentration to vary within a range of about 170 to 300 parts per million (ppm). The concentration of CO₂ in the atmosphere has increased by roughly 35 percent since the start of the industrial revolution. Globally, over the past several decades, about 80 percent of human-induced CO₂ emissions came from the burning of fossil fuels, while about 20 percent resulted from deforestation and associated agricultural practices. In the absence of strong control measures, emissions projected for this century would result in the CO₂ concentration increasing to a level that is roughly 2 to 3 times the highest level occurring over the glacial-interglacial era that spans the last 800,000 or more years.

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Energy from the Sun Has Not Increased

Global surface temperature (top, blue) and the Sun's energy received at the top of Earth's atmosphere (red, bottom). Solar energy has been measured by satellites since 1978.

The amount of solar energy received at the top of our atmosphere has followed its natural 11-year cycle of small ups and downs, but with no net increase. Over the same period, global temperature has risen markedly. This indicates that it is extremely unlikely that solar influence has been a significant driver of global temperature change over several decades.

National Center for Atmospheric Research, “Drought under global warming: a review,”