Summary: The degree of global warming during the next few years might have large political effects, as the public policy debate appears to be at a critical point in its 29th year (from Hansen’s Senate testimony). Will the pause resume, or will we get rapid warming? Close examination of the monthly data will give us clues about this important question.
How can we see the short-term temperature trend?
There is no one true way to show trends in global temperature. Here are three different perspectives; all give roughly similar results. First, let’s look at a graph by NOAA of the global average surface temperature (their excellent interactive website shows data since the reliable instrument era began in 1880). The time period selected depends on what we are looking for. The following graph shows January’s. It minimizes the overall warming trend, which is concentrated in the months of May, June, & July. Click to enlarge.
The warming since 1950 — the period in which over half of the warming comes from anthropogenic causes — occurred almost entirely in two steps: 1981-83 (near the 1979-83 El Niño period) and 1998-99 (near the 1997-98 El Niño). Since then climate scientists have shown that the two century-long temperature rise has “paused” (aka the “hiatus”). There are various theories about the cause. Then came the spike of the 2015-2016 El Niño. The peak to peak rise, 1998 to 2016, was only 0.4°F.
What happens next? The El Niño might have been just a spike, after which temperatures will fall back to the 1998-2014 average — and the “pause” continues. If temperatures don’t fall back to their previous levels, then we begin a new watch. Will the 2015-16 El Niño start another stair step, with temperatures flat at a new high level? Or will temperatures begin a steady rise? The one month anomalies provide an easy if rough way to see which of these three scenarios unfolds, each having different political implications. Unfortunately, climate models cannot yet make reliable predictions for five to ten years horizons
NOAA: Global surface temperatures for January.
Purpose line added for the 1998-2014 average: the “pause”.
After the El Niño, some skeptics predicted a strong La Niña that would drop temperatures back to the levels of the pause. The major models correctly predicted that would not happen; there was only a brief weak La Niña. Starting in September, temperatures have been dropping slightly on a year-over-year basis — down 0.18°C YoY in January. It is too soon to draw any conclusions.
Satellites provide a second perspective.
For a second perspective, see the lower troposphere temperatures recorded by satellites (prepared for NASA by U AL-Huntsville). The below graph is by UAH lead scientists Roy Spencer. It tells a roughly similar story. Showing the full time series (not just January’s) gives more detail than the above graph — with more noise. It shows an El Nino spike in 2015-16, followed by a large, fast drop. Will it return to the previous plateau, start a new plateau, or begin steady growth? Click to enlarge.
The oceans give the best perspective.
In 2003 Roger Pielke Sr. said that the best measure of global warming is the total heat content of the world’s oceans (OHC). He was called a “denier”. Now ocean heat content (OHC) is the third measure of warming commonly used by climate scientists. NOAA posts this graph of annual OHC, showing the temperature anomaly vs. the reference period 1955-2006. The trend since 1970 is only 0.04°F per decade, slower than the surface atmosphere trend of 0.31°F). OHC is little affected by the weather, and clearly shows the warming trend since 1970.
Vital background about the temperature record.
“It is extremely likely (95 – 100% certain) that human activities caused more than half of the observed increase in global mean surface temperature from 1951 to 2010.”
— One of the most important conclusions of IPCC’s AR5 Working Group I.
This statement about past warming is important. But for making public policy decisions future warming we need to know the odds of various amounts of warming during the 21st century. There is no easy answer to this, let alone a consensus of climate scientists about it. So climate activists either ignore the research (such as the 4 scenarios described in AR5) or focus on the worst of these (the truly horrific RCP8.5) while ignoring its unlikely assumptions.
So far the weather has sided with the skeptics, with little of the extreme weather activists predicted. No surge of hurricanes after Katrina (despite the predictions). No sign of the methane monster. Northern hemisphere snow extent has risen since in both the Fall and the Winter. There is little evidence that we have passed one of the often declared “tipping points”.
So it is logical that — despite the efforts of government agencies, academia, and many ngo’s — the public’s policy priorities have been unaffected by the warming campaign (details here). Republican control of the Presidency, Congress, and most States makes policy action almost impossible for the next 4 years (ceteris paribus). As a result, activists are going thru the 5 stages of grief for their campaign.
Why do global temperatures rise erratically as CO2 steadily increases?
“Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system” by José A. Rial et al, in Climatic Change, July 2004.
“The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm. While this is widely accepted, there is a relatively poor understanding of the different types of nonlinearities, how they manifest under various conditions, and whether they reflect a climate system driven by astronomical forcings, by internal feedbacks, or by a combination of both. …”
Update: new paper addresses this exact question
“Reconciling the signal and noise of atmospheric warming on decadal timescales” by Roger N. Jones and James H. Ricketts in Earth Systems Dynamics, 16 March 2017 — Abstract (red emphasis added)…
“Interactions between externally forced and internally generated climate variations on decadal timescales is a major determinant of changing climate risk. Severe testing is applied to observed global and regional surface and satellite temperatures and modelled surface temperatures to determine whether these interactions are independent, as in the traditional signal-to-noise model, or whether they interact, resulting in step-like warming. The multistep bivariate test is used to detect step changes in temperature data. The resulting data are then subject to six tests designed to distinguish between the two statistical hypotheses, hstep and htrend.
- “Test 1: since the mid-20th century, most observed warming has taken place in four events: in 1979/80 and 1997/98 at the global scale, 1988/89 in the Northern Hemisphere and 1968–70 in the Southern Hemisphere. Temperature is more step-like than trend-like on a regional basis. Satellite temperature is more step-like than surface temperature. Warming from internal trends is less than 40 % of the total for four of five global records tested …
- “Test 2: correlations between step-change frequency in observations and models (1880–2005) are 0.32 (CMIP3) and 0.34 (CMIP5). For the period 1950–2005, grouping selected events (1963/64, 1968–70, 1976/77, 1979/80, 1987/88 and 1996–98), the correlation increases to 0.78.
- “Test 3: steps and shifts (steps minus internal trends) from a 107-member climate model ensemble (2006–2095) explain total warming and equilibrium climate sensitivity better than internal trends.
- “Test 4: in three regions tested, the change between stationary and non-stationary temperatures is step-like and attributable to external forcing.
- “Test 5: step-like changes are also present in tide gauge observations, rainfall, ocean heat content and related variables.
- “Test 6: across a selection of tests, a simple stepladder model better represents the internal structures of warming than a simple trend, providing strong evidence that the climate system is exhibiting complex system behaviour on decadal timescales. This model indicates that in situ warming of the atmosphere does not occur; instead, a store-and-release mechanism from the ocean to the atmosphere is proposed. It is physically plausible and theoretically sound.
“The presence of step-like – rather than gradual – warming is important information for characterising and managing future climate risk.”
For More Information
If you liked this post, like us on Facebook and follow us on Twitter. For more information about this vital issue see the keys to understanding climate change and these posts about the politics of climate change…
- Important: climate scientists can restart the climate change debate – & win.
- How we broke the climate change debates. Lessons learned for the future.
- A story of the climate change debate. How it ran; why it failed.
- Science into agitprop: “Climate Change Is Strangling Our Oceans”.
- Ignoring science to convince the public that we’re doomed by climate change.
- Put the stories about record 2016 warming in a useful context.
To learn more about the state of climate change…
… see The Rightful Place of Science: Disasters and Climate Change
“In recent years the media, politicians, and activists have popularized the notion that climate change has made disasters worse. But what does the science actually say? Roger Pielke, Jr. takes a close look at the work of the Intergovernmental Panel on Climate Change, the underlying scientific research, and the data to give you the latest science on disasters and climate change. What he finds may surprise you and raise questions about the role of science in political debates.”