What's the difference between the Maunder Minimum and the late twentieth century?

Somehow I became distracted by an online "discussion" in which someone was confused about the connections between solar variability and climate variability. The result of that distraction was that I made a plot, shown here, that compares the Maunder Minimum (1645 - 1715 CE) to the last 60ish years (1945-present). Below is the text I wrote to present this figure, along with data sources and citations. 

Let's compare the Maunder Minimum with the second half of the 20th Century. Since there isn't really that much data, we are limited to a few quantities. I have chosen two, one is the total solar irradiance (TSI), which is the energy received by the Earth from the sun (per time per area, expressed in Watts per square meter). This data comes from a reconstruction by Wang et al. (2005) as modified by Kopp & Lean (2011), and was obtained at the link below. This data is very similar to other reconstructions (Lean et al. 2004, 2000, 1995), but is basically shifted downward by about 5 W/m2 as a recalibration. The updated data covers 1610 to 2011. The second quantity we can investigate is the northern hemisphere temperature anomaly (degrees C). There are not direct observations (of sufficient quality) reaching back to the Maunder Minimum, so we will use the temperature reconstruction of Moberg et al. (2005). That data actually stops at 1979, but we can visually extend the data to near present day by including the observed northern hemisphere temperature anomaly from Smith et al. (2008) which reaches to January 2012. For the Smith et al. data, I chose to use the land plus ocean values. There is an issue with baselines, the Moberg et al. data are anomalies with respect to the 1961-1990 average temperature while the Smith et al. data are with respect to the 1901-2000 average temperature (which is cooler than the shorter, later average). I have not adjusted for this offset, and the result is that the pink dots in the figure should actually all be slightly upward compared to the red line. The agreement between the overlapping interval is quite good, but would be a little worse if the shift were included. There are other reconstructions available, and I have no reason to choose Moberg's over the others except that it is perhaps the most recent. The TSI and temperature reconstruction data are both annual, and I've made sure the data are centered within each year. The Smith et al. data are monthly (which is why I need to center the annual records). 

Finally, just for completeness, I define the Maunder Minimum using the definition on the Wikipedia page, which is 1645 to 1715. This is in line with the TSI data. For the more recent climate, I chose to simply shift 300 years into the future. So the plots cover 1945 to 2015, but the data sets stop at whatever their last times are. The Maunder Minimum times and data are shown in blue, while the 20th/21st Century data are shown in red and pink with the time labeled along the top of each panel. 

To try to head off any misinterpretation of this plot, let me simply state what it shows. During the Maunder Minimum, there was reduced solar activity and the average northern hemisphere temperature was about 0.6 C cooler than the the 1961-1990 average value. During the period covering 1945 to the 1960s/1970s, the northern hemisphere temperatures were relatively flat and near their 20th Century average. Over those years, the sun was active, showing "normal" sunspot and TSI 11-year cycles. From some time in the 1970s until present, shown in the pink circles, the northern hemisphere average temperature shows a clear upward trend. All the monthly average values after 1996 are warmer than the 20th Century average. During this rapid and clear warming, the solar activity was typical, and quite similar to the 1945-1975 period, showing clear quasi-periodic activity. There appears to be little connection between variation in solar activity and variation in northern hemisphere average temperature during the late 20th Century. 

REFERENCES

Kopp & Lean (Geophysical Research Letters, 38, L01706, doi:10.1029/2010GL045777, 2011)

Lean, J.. 2004: Solar Irradiance Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology. Data Contribution Series # 2004-035. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

Lean, J. 2000: Evolution of the Sun's Spectral Irradiance Since the Maunder Minimum. Geophysical Research Letters, Vol. 27, No. 16, pp. 2425-2428, Aug. 15, 2000. 

Lean, J., J. Beer, and R. Bradley. 1995: Reconstruction of Solar Irradiance Since 1610: Implications for Climate Change. Geophysical Research Letters, v.22, No. 23, pp 3195-3198, December 1, 1995.

Moberg, A., D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén. 2005: Highly variable Northern Hemisphere temperatures reconstructed from low-and high-resolution proxy data. Nature, Vol. 433, No. 7026, pp. 613-617, 10 February 2005. 

Wang, Lean, and Sheeley (The Astrophysical Journal, 625:522-538, 2005 May 20)

DATA SOURCES
TSI: http://lasp.colorado.edu/sorce/data/tsi_data.htm
TSI: http://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/solar_variability/lean2000_irradiance.txt
NH T Reconstruction: http://www.ncdc.noaa.gov/paleo/pubs/moberg2005/moberg2005.html
NH T Observations: http://www.ncdc.noaa.gov/cmb-faq/anomalies.php

Is this what news sounds like?

Working from home today, I spent some time with the TV on (CNN & MSNBC) and with the radio (NPR) on. Why did I have to read about the agreement between Munich Re and other companies to proceed with plans to build large-scale solar power plants across north Africa on a environmental blog? Thank goodness Grist exists to give at least a little coverage to the story [LINK]. This is a follow up to a previous entry on this blog.

The gist of the story is that the meeting appears to be a success, and the plan is for a 400billion Euro investment ( over how long I can't tell). It sounds like a lot, but according to the story, these solar power plants would account for 15% of Europe's power by 2050. Plus, it would provide a substantial amount of power to the countries of northern Africa. A reliable, reasonably affordable, source of electricity (and employment) would certainly help stabilize the local economical and political environments across the region. I hope that their timeline is conservative, as it would be much more exciting if they could get these plants online by, say, 2020, at least supplying some electricity to Europe.

There are critics according the article. The only one they cite is a German whose argument appears to be, why do this in north Africa and not Germany. Honestly, that is pretty lame. There are certainly prospects for solar energy in Germany, but they can't compare with subtropical Africa in terms of amount of sunshine and amount of open area. Secondly, if that's the only complaint, I hope these critics get together and put some money up to start building solar power plants in Germany; that would be terrific.

I can not express how exciting I think this project is. The fact that there are huge industry backers speaks to the potential benefits as well as profits. That the plan is long-term means that there won't be short-term disappointment when there isn't much progress in the planning stages (people get disappointed so fast, e.g., the American public's dissatisfaction with the pace of the Recover Act money being distributed). Plus, this project will push the technologies involved, especially those HVDC cables, into more affordable and reliable products. A bonus would be if some American companies took notice and started seriously working on a similar solution for both North and South America.

Munich Re -- the new sun god?

An exciting development in the development of large scale solar power is an upcoming meeting initiated by reinsurance company Munich Re [LINK]. The giant company is pulling interested parties together to, apparently seriously, discuss possibilities of building a series of large solar thermal plants in northern Africa and the Arabian peninsula and transmitting the power via high-voltage, direct-current (HVDC) cables.

This isn't a new idea, but the fact that such a gigantic company is getting serious about it is a positive direction. It's an expensive proposition, especially because of the HVDC cables, which would run all the way to Europe (at least). But if these companies can actually put up some capital and show that the system works, then I'm sure the idea would spread and governments in North America and Asia would get involved. (Is it all too late? Maybe, but let's try to be a little optimistic today.)

(Okay, the normal spelling of the Egyptian sun god is Ra, but Re is an acceptable alternate spelling [LINK].)