AGW Observer

Observations of anthropogenic global warming

New research from last week 30/2011

Posted by Ari Jokimäki on August 1, 2011

Here is the new research published last week. I’m not including everything that was published but just some papers that got my attention. Those who follow my Facebook page (and/or Twitter) have already seen most of these, as I post these there as soon as they are published. Here, I’ll just put them out in one batch. Sometimes I might also point out to some other news as well, but the new research will be the focus here. Here’s the archive for the news of previous weeks. By the way, if this sort of thing interests you, be sure to check out A Few Things Illconsidered, they have a weekly posting containing lots of links to new research and other climate related news. Planet 3.0 also reports new research.

Published last week:

Circumpolar greening may provide positive feedback to warming

Greening in the circumpolar high-latitude may amplify warming in the growing season – Jeong et al. (2011) “We present a study that suggests greening in the circumpolar high-latitude regions amplifies surface warming in the growing season (May–September) under enhanced greenhouse conditions. The investigation used a series of climate simulations with the Community Atmospheric Model version 3—which incorporates a coupled, dynamic global vegetation model—with and without vegetation feedback, under both present and doubled CO2 concentrations. Results indicate that climate warming and associated changes promote circumpolar greening with northward expansion and enhanced greenness of both the Arctic tundra and boreal forest regions. This leads to additional surface warming in the high-latitudes in the growing season, primarily through more absorption of incoming solar radiation. The resulting surface and tropospheric warming in the high-latitude and Arctic regions weakens prevailing tropospheric westerlies over 45–70N, leading to the formation of anticyclonic pressure anomalies in the Arctic regions. These pressure anomalies resemble the anomalous circulation pattern during the negative phase of winter Arctic Oscillation. It is suggested that these circulation anomalies reinforce the high-latitude and Arctic warming in the growing season.” Jee-Hoon Jeong, Jong-Seong Kug, Baek-Min Kim, Seung-Ki Min, Hans W. Linderholm, Chang-Hoi Ho, David Rayner, Deliang Chen and Sang-Yoon Jun, Climate Dynamics, DOI: 10.1007/s00382-011-1142-x.

Few years without upper ocean warming is not exceptional

Tracing the upper ocean’s “missing heat” – Katsman & van Oldenborgh (2011) “Over the period 2003–2010, the upper ocean has not gained any heat, despite the general expectation that the ocean will absorb most of the Earth’s current radiative imbalance. Answering to what extent this heat was transferred to other components of the climate system and by what process(-es) gets to the essence of understanding climate change. Direct heat flux observations are too inaccurate to assess such exchanges. In this study we therefore trace these heat budget variations by analyzing an ensemble of climate model simulations. The analysis reveals that an 8-yr period without upper ocean warming is not exceptional. It is explained by increased radiation to space (45%), largely as a result of El Niño variability on decadal timescales, and by increased ocean warming at larger depths (35%), partly due to a decrease in the strength of the Atlantic meridional overturning circulation. Recently-observed changes in these two large-scale modes of climate variability point to an upcoming resumption of the upward trend in upper ocean heat content.” Katsman, C. A., and G. J. van Oldenborgh (2011), Geophys. Res. Lett., 38, L14610, doi:10.1029/2011GL048417. [Full text]

Global warming changes groundwater dynamics in permafrost melt regions

Exchange of groundwater and surface-water mediated by permafrost response to seasonal and long term air temperature variation – Ge et al. (2011) “Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3°C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment.” Ge, S., J. McKenzie, C. Voss, and Q. Wu (2011), Geophys. Res. Lett., 38, L14402, doi:10.1029/2011GL047911.

Early summer intense typhoons new feature of North Pacific since 2000

An abrupt increase of intense typhoons over the western North Pacific in early summer – Tu et al. (2011) “The frequency and intensity of typhoons have been a focus in studying typhoon-related climate changes. In this study, we focus on a seasonal cycle of intense typhoons (category 4 and 5) over the western North Pacific, particularly changes in the number of intense typhoons in early summer. In general, 81% of intense typhoons occur in July–November (JASON), with maxima in September and October. Our analysis shows that intense typhoons have tended to occur more frequently in May since the year 2000. Before 2000, intense typhoons seldom occurred in May, with a frequency of around once per decade. After 2000, however, the frequency of intense typhoons has become much higher in May—almost once per year. We have also examined changes in the large-scale environment in the past few decades. The results show that the large-scale environment did become more favorable for intense typhoons in the 2000s, which is consistent with a larger tropical cyclone genesis index. The changes include warmer sea surface temperature, higher sea surface height, larger upper-ocean heat content, weaker vertical wind shear, increased tropospheric water vapor, and greater water vapor in the mid-troposphere. The last two might be more important than the others.” Jien-Yi Tu et al 2011 Environ. Res. Lett. 6 034013 doi: 10.1088/1748-9326/6/3/034013. [Full text]

How fast oceans reach thermal equilibrium?

Equilibrium thermal response timescale of global oceans – Yang & Zhu (2011) “The equilibrium response timescale of global oceans is estimated in a fully coupled climate model. In general, the equilibrium timescale increases with depth, except in the polar region. The timescale is approximately 200 years for the ocean for depths above 1 km, and it increases to 1500 years at a depth of 3 km. A layer with a rapid timescale change, referred to as a temporacline, is located at a depth of 1.5–2 km, which is analogous to the permanent thermocline in the ocean. The equilibrium timescale varies with the sign of the change in radiative forcing. The ocean response to surface cooling could be twice as fast as the surface warming because of enhanced vertical mixing, convection and overturning circulation. However, this phenomenon only occurs below the Atlantic temporacline. For the Atlantic upper ocean, the timescale is longer in the cooling case because of the readjustment of the upper ocean to the enhanced Atlantic overturning circulation. In the Pacific, the timescale change in the warming and cooling cases is not as significant as in the Atlantic because of the lack of deep convection.” Yang, H., and J. Zhu (2011), Geophys. Res. Lett., 38, L14711, doi:10.1029/2011GL048076.

Expected adaptation to global warming observed in Cepaea nemoralis

Evolutionary change in Cepaea nemoralis shell colour over 43 years – Ożgo & Schilthuizen (2011) “We compared shell colour forms in the land snail Cepaea nemoralis at 16 sites in a 7 × 8 km section of the Province of Groningen, the Netherlands, between 1967 and 2010. To do so, we used stored samples in a natural history collection and resampled the exact collection localities. We found that almost all populations had experienced considerable evolutionary change in various phenotypes, possibly due to population bottlenecks and habitat change after repeated land consolidation schemes in the area. More importantly, we found a consistent increase in yellow effectively unbanded snails at the expense of brown snails. This is one of the expected adaptations to climate change (this area of The Netherlands has warmed by 1.5 – 2.0 °C over the time period spanned by the two sampling years), and the first clear demonstration of this in C. nemoralis.” Małgorzata Ożgo, Menno Schilthuizen, Global Change Biology, DOI: 10.1111/j.1365-2486.2011.02514.x.

When will global warming show up locally?

Early onset of significant local warming in low latitude countries – Mahlstein et al. (2011) “The Earth is warming on average, and most of the global warming of the past half-century can very likely be attributed to human influence. But the climate in particular locations is much more variable, raising the question of where and when local changes could become perceptible enough to be obvious to people in the form of local warming that exceeds interannual variability; indeed only a few studies have addressed the significance of local signals relative to variability. It is well known that the largest total warming is expected to occur in high latitudes, but high latitudes are also subject to the largest variability, delaying the emergence of significant changes there. Here we show that due to the small temperature variability from one year to another, the earliest emergence of significant warming occurs in the summer season in low latitude countries (≈25°S–25°N). We also show that a local warming signal that exceeds past variability is emerging at present, or will likely emerge in the next two decades, in many tropical countries. Further, for most countries worldwide, a mean global warming of 1 °C is sufficient for a significant temperature change, which is less than the total warming projected for any economically plausible emission scenario. The most strongly affected countries emit small amounts of CO2 per capita and have therefore contributed little to the changes in climate that they are beginning to experience.” I Mahlstein et al 2011 Environ. Res. Lett. 6 034009 doi: 10.1088/1748-9326/6/3/034009. [Full text]

Urban warming has been higher than greenhouse warming over South Korea

Quantitative Estimates of Warming by Urbanization in South Korea over the Past 55 Years (1954-2008) – Kim & Kim (2011) “The quantitative values of the urban warming effect over city stations in the Korean peninsula were estimated by using the warming mode of Empirical Orthogonal Function (EOF) analysis of 55 years of temperature data, from 1954 to 2008. The estimated amount of urban warming was verified by applying the multiple linear regression equation with two independent variables: the rate of population growth and the total population. Through the multiple linear regression equation, we obtained a significance level of 0.05% and a coefficient of determination of 0.60. This means that it is somewhat liable to the estimated effects of urbanization, in spite of the settings of some supposition. The cities that show great warming due to urbanization are Daegu, Pohang, Seoul, and Incheon, which show values of about 1.35, 1.17, 1.16, and 1.10°C, respectively. The areas that showed urban warming less than 0.2°C are Chupungnyeong and Mokpo. On average, the total temperature increase over South Korea was about 1.37 °C; the amount of increase caused by the greenhouse effect is approximately 0.60 °C, and the amount caused by urban warming is approximately 0.77 °C.” Maeng-Ki Kim and Seonae Kim, Atmospheric Environment, doi:10.1016/j.atmosenv.2011.07.028.

Middle Würmian in the Alps had to be warmer than it is today

Was the Middle Würmian in the High Alps warmer than today? – Döppes et al. (2011) “This study presents a cohesive review of the existing radiometric data as well as morphological and genetic analysis of bear remains from ten high-alpine caves, mostly from the Middle Würmian Interstadial complex, roughly corresponding to the marine isotope stage (MIS) 3 and dating back between 65,000-30,000 years before present. Today these caves are located in an area without any vegetation, which could not provide the herbivorous bears with sufficient food resources. It therefore can be concluded that the Middle Würmian in the Alps had to be warmer than it is today. Furthermore, congruent and conflicting data from soil formation in loess sequences as well as sinter data in caves are discussed in more detail to evaluate this hypothesis.” Doris Döppes, Gernot Rabeder and Mathias Stiller, Quaternary International, doi:10.1016/j.quaint.2011.07.029.

Regionally Antarctic sea ice trends agree with surface temperature trends

Sea ice trends in the Antarctic and their relationship to surface air temperature during 1979–2009 – Shu et al. (2011) “Surface air temperature (SAT) from four reanalysis/analysis datasets are analyzed and compared with the observed SAT from 11 stations in the Antarctic. It is found that the SAT variation from Goddard Institute for Space Studies (GISS) is the best to represent the observed SAT. Then we use the sea ice concentration (SIC) data from satellite measurements, the SAT data from the GISS dataset and station observations to examine the trends and variations of sea ice and SAT in the Antarctic during 1979–2009. The Antarctic sea ice extent (SIE) shows an increased trend during 1979–2009, with a trend rate of 1.36 ± 0.43% per decade. Ensemble empirical mode decomposition analysis shows that the rate of the increased trend has been accelerating in the past decade. Antarctic SIE trend depends on the season, with the maximum increase occurring in autumn. If the relationship between SIC and GISS SAT trends is examined regionally, Antarctic SIC trends agree well with the local SAT trends in the most Antarctic regions. That is, Antarctic SIC and SAT show an inverse relationship: a cooling (warming) SAT trend is associated with an upward (downward) SIC trend. It is also concluded that the relationship between sea ice and SAT trends in the Antarctic should be examined regionally rather than integrally.” Qi Shu, Fangli Qiao, Zhenya Song and Chunzai Wang, Climate Dynamics, DOI: 10.1007/s00382-011-1143-9. [Full text]

One Response to “New research from last week 30/2011”

  1. Jesús R. said

    “Regionally Antarctic sea ice trends agree with surface temperature trends”

    Curiously (for the lay person), they inversely agree😉
    A good article on the likely explanations:
    http://www.nasa.gov/topics/earth/features/antarctic_melting.html

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