Guest post by David Middleton
The current draft of the report can be found here:
Fourth National Climate Assessment (NCA4), Fifth-Order Draft (5OD)
After a cursory review of the document, a few items are worth noting.
Representative Concentration Pathways (RCPs)
A third difference between the RCPs and previous scenarios is that while none of the SRES scenarios included a scenario with explicit policies and measures to limit climate forcing, all of the three lower RCP scenarios (2.6, 4.5, and 6.0) are climate-policy scenarios. At the higher end of the range, the RCP8.5 scenario corresponds to a future where carbon and methane emissions continue to rise as a result of fossil fuel use, albeit with significant declines in emission growth rates over the second half of the century (Figure 4.1), significant reduction in aerosols, and modest improvements in energy intensity and technology (Riahi et al. 2011). Atmospheric carbon dioxide levels for RCP8.5 are similar to those of the SRES A1fi scenario: they rise from current-day levels of 400 up to 936 parts per million (ppm). CO2 16 -equivalent levels (including emissions of other non-CO2 17 greenhouse gases, aerosols, and other substances that affect climate) reach more than 1200 ppm by 2100, and global temperature is projected to increase by 5.4°–9.9°F (3°–5.5°C) by 2100 relative to the 1986–2005 average. RCP8.5 reflects the upper range of the open literature on emissions, but is not intended to serve as an upper limit on possible emissions nor as a business-as-usual or reference scenario for the other three scenarios.
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First the good news:
“RCP8.5… is not intended to serve as… a business-as-usual or reference scenario.”
That said, a text search of the document returned the following:
| Representative Concentration Pathways | |
| Scenario | Occurrences |
| RCP2.6, RCP 2.6 | 17 |
| RCP4.5, RCP 4.5 | 32 |
| RCP8.5, RCP 8.5 | 75 |
One might think that the business-as-usual or reference scenario would be the most commonly referenced scenario. However, RCP 8.5 is referenced more than all the other scenarios combined. While RCP 6.0, “a mitigation scenario, meaning it includes explicit steps to combat greenhouse gas emissions (in this case, through a carbon tax)” which most closely matches “business-as-usual,” is only referenced once.
A Sampling of Key Findings
3. Detection and Attribution of Climate Change
Key Findings
1. The likely range of the human contribution to the global mean temperature increase over the period 1951–2010 is 1.1° to 1.4°F (0.6° to 0.8°C), and the central estimate of the observed warming of 1.2°F (0.65°C) lies within this range (high confidence). This translates to a likely human contribution of 93%–123% of the observed 1951–2010 change. It is extremely likely that more than half of the global mean temperature increase since 1951 was caused by human influence on climate (high confidence). The likely contributions of natural forcing and internal variability to global temperature change over that period are minor (high confidence).
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Over the past 2,000 years, the average temperature of the Northern Hemisphere has exceeded natural variability (defined as two standard deviations from the pre-1865 mean) three times: 1) the peak of the Medieval Warm Period 2) the nadir of the Little Ice Age and 3) since 1998. Human activities were unlikely to have been the cause of the first two deviations. 70% of the warming since the early 1600’s clearly falls within the range of natural variability.
Figure 2. Temperature reconstruction (Ljungqvist, 2010), northern hemisphere instrumental temperature (HadCRUT4) and Law Dome CO2 (MacFarling Meure et al., 2006). Temperatures are 30-yr averages to reflect changing climatology. (The Good, the Bad and the Null Hypothesis)
On a climatology basis, the modern warming only exceeds Common Era pre-industrial natural variability by a maximum of 0.216° C
Figure 3. The modern warming only exceeds Common Era pre-industrial natural variability by a maximum of 0.216° C. So, it is highly unlikely that the “range of the human contribution to the global mean temperature increase over the period 1951–2010 is 1.1° to 1.4°F (0.6° to 0.8°C).”
6. Temperature Changes in the United States
KEY FINDINGS
1. Average annual temperature over the contiguous United States has increased by 1.2°F (0.7°C) for the period 1986–2016 relative to 1901–1960 and by 1.8°F (1.0°C) based on a linear regression for the period 1895–2016 (very high confidence). Surface and satellite data are consistent in their depiction of rapid warming since 1979 (high confidence). Paleo-temperature evidence shows that recent decades are the warmest of the past 1,500 years (medium confidence).
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“Medium confidence” is equivalent to a Scientific Wild-Ass Guess (SWAG).
Figure 4. NCA4 Confidence levels, page 10.
The lame-stream media took “suggestive evidence, limited consistency, models incomplete, methods emerging, competing schools of thought and turned it into a statement of fact:
Just as troubling were draft findings destined for the quadrennial National Climate Assessment. Scientists from 13 federal agencies found that a rapid rise in temperatures since the 1980s in the United States represents the warmest period in 1,500 years.
A “medium confidence” Mannian Hockey Stick became: “Scientists from 13 federal agencies found that a rapid rise in temperatures since the 1980s in the United States represents the warmest period in 1,500 years.”
They based this assertion on one hockey-stick climate reconstruction, Mann et al., 2008.
Figure 5. NCA4 Figure 1.8 Mann et al., 2008. Even with this Hockey Stick, the modern warming only exceeded pre-industrial natural variability by 0.5° F (0.3° C). At least they had the decency to clearly identify where they spliced in the instrumental data.
None of the spectrally consistent reconstructions (Moberg, Esper, Ljungqvist, etc. were cited)… I wonder why?
So, what would it mean, if the reconstructions indicate a larger (Esper et al., 2002; Pollack and Smerdon, 2004; Moberge t al., 2005) or smaller (Jones et al., 1998; Mann et al., 1999) temperature amplitude? We suggest that the former situation, i.e. enhanced variability during pre-industrial times, would result in a redistribution of weight towards the role of natural factors in forcing temperature changes, thereby relatively devaluing the impact of anthropogenic emissions and affecting future predicted scenarios. If that turns out to be the case, agreements such as the Kyoto protocol that intend to reduce emissions of anthropogenic greenhouse gases, would be less effective than thought.
Figure 6. When the uncertainty range of the proxy data is honored, it cannot be stated that the rate of recent warming is unprecedented.
12. Sea Level Rise
KEY FINDINGS
1. Global mean sea level (GMSL) has risen by about 7–8 inches (about 16–21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993 (very high confidence). Human-caused climate change has made a substantial contribution to GMSL rise since 1900 (high confidence), contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years (medium confidence).
2. Relative to the year 2000, GMSL is very likely to rise by 0.3–0.6 feet (9–18 cm) by 2030, 0.5–1.2 feet (15–38 cm) by 2050, and 1 to 4 feet (30–130 cm) by 2100 (very high confidence in lower bounds; medium confidence in upper bounds for 2030 and 2050; low confidence in upper bounds for 2100). Future emissions pathways have little effect on projected GMSL rise in the first half of the century, but significantly affect projections for the second half of the century (high confidence). Emerging science regarding Antarctic ice sheet stability suggests that, for high emission scenarios, a GMSL rise exceeding 8 feet (2.4 m) by 2100 is physically possible, although the probability of such an extreme outcome cannot currently be assessed. Regardless of emissions pathway, it is extremely likely that GMSL rise will continue beyond 2100 (high confidence).
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“Global mean sea level (GMSL) has risen by about 7–8 inches (about 16–21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993 (very high confidence)”… And?
Sea level has been rising at a secular rate of about 1.9 mm/yr since the end of neoglaciation (~1860 AD).
Figure 7. Sea Level Reconstruction (Jevrejeva et al., 2014), More Fun With Sea Level
About 3 inches of sea level rise has occurred since 1993. About 4 inches of sea level rise occurred from 1930-1950. There was very little sea level rise from 1951-1992.
Figure 8. Same as above with multi-decadal fluctuations highlighted.
“Human-caused climate change has made a substantial contribution to GMSL rise since 1900 (high confidence)”… Based on what???
“Contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years (medium confidence)”… Another SWAG based on another hockey stick (Kopp et al., 2016).
Figure 9. NCA4 Figure ES.8a, page 27. Sea level reconstruction (Kopp et al., 2016). A 12-in (30 cm) ruler has been overlaid on the image for scale. This hockey stick splice tide gauge data onto low frequency proxy data. Even with the resolution discrepancy, modern sea level is only 2.5 inches higher than pre-industrial natural variability – during neoglaciation. When uncertainty is honored, the rate of instrumental era sea level rise is not significantly different than pre-industrial time.
“Relative to the year 2000, GMSL is very likely to rise by 0.3–0.6 feet (9–18 cm) by 2030, 0.5–1.2 feet (15–38 cm) by 2050, and 1 to 4 feet (30–130 cm) by 2100 (very high confidence in lower bounds; medium confidence in upper bounds for 2030 and 2050; low confidence in upper bounds for 2100).”
At least they get this one somewhat correct.
“Relative to the year 2000, GMSL is very likely to rise by… 1 to 4 feet (30–130 cm) by 2100 (very high confidence in lower bounds… low confidence in upper bounds for 2100)”
Sea level is very likely to rise a bit less than 1 foot over the remainder of this century.
Figure 10. Sea level is very likely to rise by an additional 7-11 inches over the remainder of this century. 3 additional feet of sea level rise wold require an acceleration to a rate twice that of the Holocene Transgression. Oh say can you see modern sea level rise from a geological perspective?
Figure ES.8b is simply bat schist crazy.
Figure 11. NCA4 Figure ES.8b with Figure 11 overlaid. Red is RCP 8.5. The blue curve, an intermediate RCP, would necessitate >20 mm/yr of SLR in the late 21st century.
And, of course, the lame-stream media turns this into…
The report, by more than 450 scientists from 60 nations, also found that greenhouse gases in the atmosphere and global sea levels are at their highest levels on record.
It all depends on when you start the record.
Figure 12. Oh say can you see modern sea level rise from a geological perspective?
Life in the Adjustocene
Yesterday, I authored a post about NCA3’s model projections and I noted that the observations had falsified their models…
Figure 13. NCA3 models run hot… as always.
Well, it appears that NCA4 will address this issue by adjusting the observations to match the models…
Figure 14. NCA Figure ES.3, page 70 compared to NCA3.
They adjusted the observations to match the model in the current draft report.
Figure 15. Livin’ la vida Adjustocene!
NCA4 shows the observations tracking the model-mean prior to the 2016 El Niño and then spiking above the mean during it. Nick Stokes provided the following image in one of his very astute comments:
Figure 16. Observations spiking to the CMIP5 mean during (Comment by Nick Stokes). Note: I am not implying that Nick Stokes agrees with anything I’ve ever posted or endorsing anything. I am simply crediting him with providing this image.
Conclusions
NCA4 paints a picture of the climate basically behaving within the general bounds of Late Holocene natural variability, accompanied by lots of rhetoric about being certain that humans have caused at least half of whatever happened since 1950…
“Same as it ever was”…
