Observational constraints on the effective climate sensitivity from the historical period

The observed warming in the atmosphere and ocean can be used to estimate the climate sensitivity linked to present-day feedbacks, which is referred to as the effective climate sensitivity (Shist ). However, such an estimate is affected by uncertainty in the radiative forcing, particularly aerosols, over the historical period. Here, we make use of detection and attribution techniques to derive the surface air temperature and ocean warming that can be attributed directly to greenhouse gas increases. These serve as inputs to a simple energy budget to infer the likelihood of Shist in response to observed greenhouse gases increases over two time periods (1862–2012 and 1955–2012). The benefit of using greenhouse gas attributable quantities is that they are not subject to uncertainties in the aerosol forcing (other than uncertainty in the attribution to greenhouse gas versus aerosol forcing not captured by the multi-model aerosol response pattern). The resulting effective climate sensitivity estimate, Shist , ranges from 1.3 °C to 3.1 °C (5%–95% range) over the full instrumental period (1862–2012) for our best estimate, and gets slightly wider when considering further uncertainties. This estimate increases to 1.7 °C–4.6 °C if using the shorter period (1955–2012). We also evaluate the climate model simulated surface air temperature and ocean heat content increase in response to greenhouse gas forcing over the same periods, and compare them with the observationally-constrained values. We find that that the ocean warming simulated in greenhouse gas only simulations in models considered here is consistent with that attributed to greenhouse gas increases from observations, while one model simulates more greenhouse gas-induced surface air warming than observed. However, other models with sensitivity outside our range show greenhouse gas warming that is consistent with that attributed in observations, emphasising that feedbacks during the historical period may differ from the feedbacks at CO2 doubling and from those at true equilibrium

Possible causes of data model discrepancy in the temperature history of the last Millennium

Model simulations and proxy-based reconstructions are the main tools for quantifying pre-instrumental climate variations. For some metrics such as Northern Hemisphere mean temperatures, there is remarkable agreement between models and reconstructions. For other diagnostics, such as the regional response to volcanic eruptions, or hemispheric temperature differences, substantial disagreements between data and models have been reported. Here, we assess the potential sources of these discrepancies by comparing 1000-year hemispheric temperature reconstructions based on real-world paleoclimate proxies with climate-model-based pseudoproxies. These pseudoproxy experiments (PPE) indicate that noise inherent in proxy records and the unequal spatial distribution of proxy data are the key factors in explaining the data-model differences. For example, lower inter-hemispheric correlations in reconstructions can be fully accounted for by these factors in the PPE. Noise and data sampling also partly explain the reduced amplitude of the response to external forcing in reconstructions compared to models. For other metrics, such as inter-hemispheric differences, some, although reduced, discrepancy remains. Our results suggest that improving proxy data quality and spatial coverage is the key factor to increase the quality of future climate reconstructions, while the total number of proxy records and reconstruction methodology play a smaller role

Recommended temperature metrics for carbon budget estimates, model evaluation and climate policy

Recent estimates of the amount of carbon dioxide that can still be emitted while achieving the Paris Agreement temperature goals are larger than previously thought. One potential reason for these larger estimates may be the different temperature metrics used to estimate the observed global mean warming for the historical period, as they affect the size of the remaining carbon budget. Here we explain the reasons behind these remaining carbon budget increases, and discuss how methodological choices of the global mean temperature metric and the reference period influence estimates of the remaining carbon budget. We argue that the choice of the temperature metric should depend on the domain of application. For scientific estimates of total or remaining carbon budgets, globally averaged surface air temperature estimates should be used consistently for the past and the future. However, when used to inform the achievement of the Paris Agreement goal, a temperature metric consistent with the science that was underlying and directly informed the Paris Agreement should be applied. The resulting remaining carbon budgets should be calculated using the appropriate metric or adjusted to reflect these differences among temperature metrics. Transparency and understanding of the implications of such choices are crucial to providing useful information that can bridge the science–policy gap

Winter amplification of the European Little Ice Age cooling by the subpolar gyre

Climate reconstructions reveal a strong winter amplification of the cooling over central and northern continental Europe during the Little Ice Age period (LIA, here defined as c. 16th-18th centuries) via persistent, blocked atmospheric conditions. Although various potential drivers have been suggested to explain the LIA cooling, no coherent mechanism has yet been proposed for this seasonal contrast. Here we demonstrate that such exceptional wintertime conditions arose from sea ice expansion and reduced ocean heat losses in the Nordic and Barents seas, driven by a multicentennial reduction in the northward heat transport by the subpolar gyre (SPG). However, these anomalous oceanic conditions were largely decoupled from the European atmospheric variability in summer. Our novel dynamical explanation is derived from analysis of an ensemble of last millennium climate simulations, and is supported by reconstructions of European temperatures and atmospheric circulation variability and North Atlantic/Arctic paleoceanographic conditions. We conclude that SPG-related internal climate feedbacks were responsible for the winter amplification of the European LIA cooling. Thus, characterization of SPG dynamics is essential for understanding multicentennial variations of the seasonal cycle in the European/North Atlantic sector

Potential volcanic impacts on future climate variability

Volcanic activity plays a strong role in modulating climate variability (ref. 1). Most model projections of the twenty-first century, however, under-sample future volcanic effects by not representing the range of plausible eruption scenarios (ref. 2,3,4). Here, we explore how sixty possible volcanic futures, consistent with ice-core records (ref. 5), impact climate variability projections of the Norwegian Earth System Model (NorESM) (ref. 6) under RCP4.5 (ref. 7). The inclusion of volcanic forcing enhances climate variability on annual-to-decadal timescales. Although decades with negative global temperature trends become ∼50% more commonplace with volcanic activity, these are unlikely to be able to mitigate long-term anthropogenic warming. Volcanic activity also impacts probabilistic projections of global radiation, sea level, ocean circulation, and sea-ice variability, the local-scale effects of which are detectable when quantifying the time of emergence (ref. 8). These results highlight the importance and feasibility of representing volcanic uncertainty in future climate assessments

Beyond equilibrium climate sensitivity

ISSN:1752-0908ISSN:1752-089

Forced and unforced decadal behavior of the interhemispheric SST contrast during the instrumental period (1881–2012): Contextualizing the late 1960s–early 1970s shift

The sea surface temperature (SST) contrast between the Northern Hemisphere (NH) and Southern Hemisphere (SH) influences the location of the intertropical convergence zone (ITCZ) and the intensity of the monsoon systems. This study examines the contributions of external forcing and unforced internal variability to the interhemispheric SST contrast in HadSST3 and ERSSTv5 observations, and 10 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) from 1881 to 2012. Using multimodel mean fingerprints, a significant influence of anthropogenic, but not natural, forcing is detected in the interhemispheric SST contrast, with the observed response larger than that of the model mean in ERSSTv5. The forced response consists of asymmetric NH–SH SST cooling from the mid-twentieth century to around 1980, followed by opposite NH–SH SST warming. The remaining best-estimate residual or unforced component is marked by NH–SH SST maxima in the 1930s and mid-1960s, and a rapid NH–SH SST decrease around 1970. Examination of decadal shifts in the observed interhemispheric SST contrast highlights the shift around 1970 as the most prominent from 1881 to 2012. Both NH and SH SST variability contributed to the shift, which appears not to be attributable to external forcings. Most models examined fail to capture such large-magnitude shifts in their control simulations, although some models with high interhemispheric SST variability are able to produce them. Large-magnitude shifts produced by the control simulations feature disparate spatial SST patterns, some of which are consistent with changes typically associated with the Atlantic meridional overturning circulation (AMOC)

AUTOMAATTISEN DIAGNOSTIIKKAJÄRJESTELMÄN SUUNNITTELU JA TOTEUTUS TUOTANNON TARPEISIIN

Opinnäytetyön tavoitteena oli suunnitella ja toteuttaa diagnostiikkajärjestelmä painevalukoneelle Alsiva Oy:n käyttöön. Järjestelmän keskeisimmät tavoitteet oli toteuttaa kappalelaskuri ja käyttöasteen laskenta kohtuullisin kustannuksin. Tiedonsiirrossa hyödynnetään yksinkertaista ohjaussignaalin logiikkaa RS-232-standardin mukaisesti. Järjestelmän toimintaan tarvittava signaali saatiin valukoneeseen rakennetulta erilliseltä kytkimeltä. Tämän ja tietokoneen väliin rakennettiin elektroninen toteutus, jossa puskuripiiri muuntaa jännitetasot sopivaksi ja joka suojaa PC:n RS-232-piiriä ylikuormitukselta. Signaalia luetaan PC:llä, johon ohjelmoitiin sovellus tietojen näyttämistä ja arkistointia varten, Visual Basic ohjelmointikieltä käyttäen. Sovellus tehtiin Microsoft Visual Studio 2008 Express -ohjelmointiympäristössä ja on tarkoitettu käytettäväksi Microsoft Windows -käyttöjärjestelmällä. Lopputuloksena saatiin toteutettua järjestelmään tarvittava kytkentä ja toimiva sovellus pienin kustannuksin. Järjestelmää voi tarvittaessa laajentaa myös muihin tuotannon painevalukoneisiin. Toimiessaan järjestelmä auttaa yritystä tuotannon koneiden käyttöasteen sekä tuotteiden valmistuksen tehokkuuden seuraamisessa.The objective of this final project in engineering was to plan and build a diagnostic system for the use of die-casting machine in Alsiva Oy. The purpose of the system was to act as product calculator and to calculate the utilization rate at moderate expenses. Simple control signal logic was used in data transmission according to the RS-232 standard. The information that was demanded by the system was measured from the separately produced switch in die-casting machine. A microcontroller buffer was designed between this switch and computer that adapts the voltage levels and protects the RS-232 circuit of the computer from overload. The signal is read by a PC, where was programmed an application to show information to the user and to archive files to PC. This program was made with Visual Basic programming language in Microsoft Visual Studio 2008 Express programming environment and is intended to be used in Microsoft Windows operating system. The outcome of the thesis was the electronic implementation and functional application at low costs. As further development the aim is to expand the system for other diecasting machines in the production plant. The system helps to solve the utilization rate of the die-casting machines and gives information about the manufacturing efficiency

Interpretations of the Paris climate target

In the 2015 UNFCCC Paris Agreement, article 2 expresses the target of “Holding the increase in global temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C … recognizing that this would significantly reduce the risks and impacts of climate change”1. Different interpretations of the precise meaning of the phrases ‘increase in global temperature’2 and ‘pre-industrial’3 could have large effects on mitigation requirements and corresponding social, policy and political responses. Here we suggest that levels of current global mean surface warming since pre-industrial times that are higher than those derived by Millar et al. could have been calculated using alternative, but equally valid, assumptions as the ones made by those authors