Global warming and climate change is also shown by a range of phenomena, hardly needing sophisticated statistics, models or abstruse observations and tests, that anyone can observe if they wish to.
- Glaciers are retreating,
- The Arctic ice is retreating and thinning
- Spring is arriving earlier
- Natural animal and plant distributions are moving pole ward
- Fires are becoming more common in every continent with forests remaining
- The pine beetle is destroying forests across North America.
- Drought and floods are savaging Australia
- Droughts are becoming more common in Africa and Asia
- Heat waves have killed thousands in India and Europe
A consequence of rising carbon dioxide concentrations, quite apart from warming, is acidification of the oceans that is destroying marine shelled animals and thus many ecosystems.
Below I show several graphs and maps that answer the main concerns of the real sceptics. Real sceptics are open minded and amenable to well presented information and ideas. Deniers are people who never change their mind and only pretend to be interested in science. Everyone should understand the information so as to be able to participate in discussions with sceptics or deniers.
Recent Global Temperature Changes
This first graph shows the yearly global temperatures changes (based on US NASA records). Notice that although the annual temperatures oscillate ( due mainly to oceanic oscillations) the overall trend continues upward. The actual 2009 figure is a bit higher than the estimate, being equal to the second highest on record.
(Graph from the Copenhagen Diagnosis, 2009)
The graph below from NASA's GISS has the exact date for 2009 showing it to be equal to four others in the last 11 years
A Decade Plateau?
Although the last ten years has not warmed dramatically (the NASA data shows a faster warming than the UK data as the UK data does not include some data from the Arctic that NASA has access to) according to both data sets it has not cooled over the last decade, and the decade as a whole was the hottest for about 120,000 years. The climate in the most vulnerable regions has not improved to the pre-industrial state or even the 1940s climate. The very high temperature in 1998 that was due to the El Nino was more than replicated in 2005 without the El Nino. Although 2008 was a relatively cool year and led to cries of a cooling Earth, 2009 was equal to the second hottest year for thousands of years.
Note that when the deniers were crying cooling they did not doubt the accuracy of the data, although from some private emails they now claim to have found inaccuracy. The slight decrease in the average rate of rise of atmospheric and shallow ocean warming may have been due to the levelling off in the rate of rise of methane concentrations (see below) and the decline in water vapour (Solomon, 2010). Another researcher suggests the relative plateau is due to aerosol and cloud effects. This science is difficult enough without bank rolled and ideological deniers distorting it.
Note other small temperature "plateaus" in the mid 1980s and early 1990s that deniers don't comment on, as significant rises have taken place since.
Ocean Heat Uptake
But what is most revealing is Murphy's 2009 study based on Domingues et al data showing that the heat content of the oceans down to 3000 metres depth continued to rise rapidly in the early naughties, well above the El Nino high of 1998. But other data since this diagram was drawn up show a relative plateauing.
But as you can note in this diagram plateauing or falls have happened several times before. We could call these the undenied plateaus (and falls) as no one draws attention to them. Note particularly the plateau of 1981-1985 that would have agitated the deniers no end if they had been around then.
(This diagram is taken from the excellent Skeptical Science website)
Whatever the exact balance of causes of the atmospheric changes in recent decades, rising global temperature in the 1990s and 2000s have raised the rate of ice sheet melting by 10 times and increased the rate of sea level rise from 2 mm to 3 mm per year.
If you feel confused, try....For Beginners and the Bewildered
Further warming from human made GHGs and surface earth system feedback will mean much more serious heat waves, droughts, forest fires, dust storms, wet storms, floods, human, crop and animal diseases, the loss of tens of thousands of species and whole ecosystems, acidification of the oceans, and sea intrusion through sea level rise, typhoons and storm surges. This could be catastrophic for our children and grandchildren not to mention further generations. It could mean that global warming could go beyond human influence and rise six or more degrees creating a state in which few humans would survive (Mark Lynas, 2008). We must start to take more serious action to avoid this fate.
Even if the last four decades of warming were largely natural, which it isn't, we must do all we can to stop it, and reduce the carbon dioxide in the atmosphere by absorption as, at least, it is going to destroy ocean ecosystems.
Is Global Warming Human?
Climate scientific theory claims that global warming in the last four decades is very largely due to human created greenhouse gases together with certain dusts, as well as natural feedbacks (see separate page: Surface Earth system feedbacks) Other dusts or aerosols are having a cooling effect. Since the evidence for significant warming became stronger, many deniers have claimed that it is due to natural causes, either increased solar radiation or increased cosmic ray penetration. They have also claimed that it is due to a human cause quite different from atmospheric gases and dusts, that of urban heat. It is interesting that I have never seen a deniers comparison of these three causes, nor a proportioning of their influence. While deniers are are united in their opposition to climate theory, they have nothing like an alternative consensus theory themselves. In the history of science, major scientific theories have only been overthrown by a better theory, not simply by rancourous oppostion.
The Effect of Solar Radiation on Global Warming
The graph below compares the solar radiation (red line) and the average global temperatures (blue line) (graph smoothed). From 1930 to 1945 an increase in solar radiation contributed markedly to global warming, but since 1980 the temperature has risen steeply but solar radiation has fallen. (after Andrew Glikson). The solar sunspot cycle is superimposed on other longer term changes that are not easily predictable. Even if we are extremely fortunate and the sun cools dramatically over the next decade or two, we will still be faced with rising acidity in the ocean and all the other over-exploitation of resources. When the cycle turns, as it must sooner or later, the heating will be catastrophic if we have not controlled green house gas and warming dusts in the meantime.
As solar and other influences are changing slightly or falling, this warming trend since 1970 can only be due to greenhouse gases (GHGs) and other pollution, and now increasing surface earth system feedback.
Do Cosmic Rays Cause Global Warming?
It has been shown recently that periodic changes in the amount of cosmic rays reaching Earth show no correlation with cloud cover. One of many examples from this research is shown below. Previously, it had been postulated that cosmic rays contributed to the formation of clouds that then contributed to, or even solely caused, global warming.
Urban Heat Island Effect
In examining the common sceptic/denier claim that global warming is due to the urban heat island effect, Coby Beck on Grist has been inspired to compared a picture of the Earth's lights at night from Astronomy Picture of the Day with NASA GISS's 2005 Surface Temperature Anomaly (see below).
As Beck says, if global warming theory is an error, as it is due to high temperature anomaly readings in urban areas, why is it that many of the major temperature anomalies identified by NASA on a world scale are largely in highly rural rather than urban areas, and vice versa. Particularly note the Arctic, south Central Africa and India.
The Range of Influences on Global Warming
Climate scientists call the range of influences on the earths energy balance that have changed since about 1750, radiative forcing. Note that in the diagram below the influences are summed for about 255 years, whereas the main debate with deniers is about the last four decades since 1970.
The energy (or power) unit is watts per square metre of the Earths surface (energy is power generated over a time period). These are not total influences but the change over roughly 255 years, instantaneously measured. The diagram below (Wikipedia after IPCC) summarizes the two types of influences, the red and yellow ones (positive) that tend to cause the Earth to warm and the blue ones (negative) that tend to cause it to cool, and the net or summary in dark red on the right. The main coloured bars indicate IPCC's best estimate for the values, while the line bars indicate the degree of uncertainty. Note that the change in natural influence from the Sun (solar irradiance) over this period is very small.
Estimates continue to change a little as new research results are published. However, some of the amounts shown here from IPCC are different from those in independent papers. Notably some scientists believe black carbon soot has a major positive radiative effect (warming) of about 0.5 W/m2 (see below) and others note the small influence of volcanoes separately.
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