Statistically derived contributions of diverse human influences to twentieth-century temperature changes

The warming of the climate system is unequivocal as evidenced by an increase in global temperatures by 0.8 °C over the past century. However, the attribution of the observed warming to human activities remains less clear, particularly because of the apparent slow-down in warming since the late 1990s. Here we analyse radiative forcing and temperature time series with state-of-the-art statistical methods to address this question without climate model simulations. We show that long-term trends in total radiative forcing and temperatures have largely been determined by atmospheric greenhouse gas concentrations, and modulated by other radiative factors. We identify a pronounced increase in the growth rates of both temperatures and radiative forcing around 1960, which marks the onset of sustained global warming. Our analyses also reveal a contribution of human interventions to two periods when global warming slowed down. Our statistical analysis suggests that the reduction in the emissions of ozone-depleting substances under the Montreal Protocol, as well as a reduction in methane emissions, contributed to the lower rate of warming since the 1990s. Furthermore, we identify a contribution from the two world wars and the Great Depression to the documented cooling in the mid-twentieth century, through lower carbon dioxide emissions. We conclude that reductions in greenhouse gas emissions are effective in slowing the rate of warming in the short term.F.E. acknowledges financial support from the Consejo Nacional de Ciencia y Tecnologia (http://www.conacyt.gob.mx) under grant CONACYT-310026, as well as from PASPA DGAPA of the Universidad Nacional Autonoma de Mexico. (CONACYT-310026 - Consejo Nacional de Ciencia y Tecnologia; PASPA DGAPA of the Universidad Nacional Autonoma de Mexico

Statistical evidence about human influence on the climate system

Working Paper No WP2012-012We use recent methods for the analysis of time series data, in particular related to breaks in trends, to establish that human factors are the main contributors to the secular movements in observed global and hemispheric temperatures series. The most important feature documented is a marked increase in the growth rates of temperatures (purged from the Atlantic Multidecadal Oscillation) and anthropogenic greenhouse gases occurring for all series around 1955, which marks the start of sustained global warming. Also evidence shows that human interventions effectively slowed global warming in two occasions. The Montreal Protocol and the technological change in agricultural production in Asia are major drivers behind the slowdown of the warming since 1994, providing evidence about the effectiveness of reducing emissions of greenhouse gases other than CO2 for mitigating climate change in the shorter term. The largest socioeconomic disruptions, the two World Wars and the Great Crash, are shown to have contributed to the cooling in the mid 20th century. While other radiative factors have modulated their effect, the greenhouse gases defined the secular movement in both the total radiative forcing and the global and hemispheric temperature series. Deviations from this anthropogenic trend are shown to have transitory effects

Modelling structural breaks in the US, UK and Japanese unemployment rates

In this paper we use a general procedure to detect structural breaks at unknown points in time which allows for different orders of integration and deterministic components in each subsample (see Gil-Alana, 2006). First, we extend it to the non-linear case, and show by means of Monte Carlo experiments that the procedure performs well in a non-linear environment. Second, we apply it to test for breaks in the unemployment rate in the US, the UK and Japan. Our results shed some light on the empirical relevance of alternative unemployment theories for these countries. Specifically, a structuralist interpretation appears more appropriate for the US and Japan, whilst a hysteresis model accounts better for the UK experience (and also for the Japanese one in the second subsanple). We interpret these findings in terms of different labour market features

Real exchange rates in latin america: The ppp hypothesis and fractional integration

This paper tests for PPP in a group of seventeen Latin American (LA) countries by applying fractional integration techniques to real exchange rate series. Compared to earlier studies on these economies, this approach has the advantage of allowing for non-integer values for the degree of integration, and thus for the possibility of PPP not holding continuously but as a long-run equilibrium condition. Further, breaks in the series are endogenously determined using a procedure based on the least-squares principle. This is particularly crucial in the Latin American countries, which have been affected by several exchange rate crises and policy regime changes. The results, based on different assumptions about the underlying disturbances, are in the majority of cases inconsistent with PPP, even more so when breaks are incorporated: Argentina is the only country for which clear evidence of mean reversion is found in the model including a break, albeit only in the second subsample

European Integration, Productivity Growth and Real Convergence

This paper derives a stochastic endogenous growth model that investigates the impact of European Union integration on convergence and productivity growth. We deviate from the general strand of literature by not only deriving a theoretical model for the effects of integration on the rate of economic growth, but also by using more appropriate estimation techniques. The outcome of a series of panel and structural break tests examining the accession process of five recent members to the Union generally show improved rates of productivity growth and convergence to EU standards. We then draw from the experience of these recent members to derive implications for the first-round EU candidate countries. Subsequent tests on the first-round candidate countries find a high level of heterogeneity in growth rates, and a fast-paced convergence to EU standards.http://deepblue.lib.umich.edu/bitstream/2027.42/40043/3/wp657.pd

Determinants of Sovereign Bond Yield Spreads in the EMU. An Optimal Currency Area Perspective

In the light of the recent financial crisis, we take a panel cointegration approach that allows for structural breaks to the analysis of the determinants of sovereign bond yield spreads in nine economies of the European Monetary Union. While we find evidence for a level break in the cointegrating relationship, we do not find empirical support for a regime shift and hence for a change in the pricing of the determinants of sovereign spreads. Moreover, results show that (i) fiscal imbalances (namely expected government debt-to-GDP differentials) are the main long-run drivers of sovereign spreads; (ii) liquidity risks and cumulated inflation differentials have non-negligible weights; but (iii) all conclusions are ultimately connected to whether or not the sample of countries is composed of members of an Optimal Currency Area (OCA). In particular, we establish (i) that results are overall driven by those countries not passing the OCA test; and (ii) that investors closely monitor and severely punish the deterioration of expected debt positions of those economies exhibiting significant gaps in competitiveness

Estimating Structural Changes in the Vertical Price Relationships in U.S. Beef and Pork Markets

This paper examines structural breaks in the vertical price relationships in U.S. beef/cattle and pork/hog sectors using monthly data of the past 40 years. A major methodological issue addressed is how to estimate price relationships when data contain intermittent structural breaks with unknown break dates. The adopted procedures endogenously search for structural break dates while explicitly accounting for this search in statistical inferences. Four breaks for the beef/cattle price relationship and three breaks for the pork/hog price relationship are identified. The estimation results further confirm the importance of allowing for structural breaks in the analysis of vertical price relationships.farm cattle and hog prices, long-run price relationship, retail beef and pork prices, structural breaks of unknown timing, structural changes, vertical price relationship, Industrial Organization, Livestock Production/Industries,

Testing PPP for the South African Rand/US Dollar exchange rate at different frequencies

This paper tests the PPP hypothesis for the South African rand/ US dollar real exchange rate using a fractional integration framework. The results suggest that the real exchange rate of the South African rand with respect to the US dollar is a highly dependent variable with an order of integration very close to 1. This finding is not affected by the data frequency considered (daily, weekly or monthly). Also, there appears to be a single break in December 2001 (possibly corresponding to a change in the monetary policy framework), with the unit root null being rejected in favour of d > 1 for the periods before the break, but not afterwards. Thus, our results strongly reject the PPP hypothesis for the South African rand / US dollar rate across data frequencies.The second-named author gratefully acknowledges financial support from the Ministerio de Ciencia y Tecnología (ECO2008-03035 ECON Y FINANZAS, Spain) and from a PIUNA Project of the University of Navarra

Long memory in German energy price indices

This study examines the long-memory properties of German energy price indices (specifically, import and export prices, as well as producer and consumer prices) for hard coal, lignite, mineral oil and natural gas adopting a fractional integration modelling framework. The analysis is undertaken using monthly data from January 2000 to August 2011. The results suggest nonstationary long memory in the series (with orders of integration equal to or higher than 1) when breaks are not allowed for. However, endogenous break tests indicate a single break in all series except for producer prices for lignite for which two breaks are detected. When such breaks are taken into account, and with autocorrelated disturbances, evidence of mean reversion is found in practically all cases.This study is partially funded by the Ministry of Education of Spain (ECO2011-2014 ECON Y FINANZAS, Spain) and from a Jeronimo de Ayanz project of the Government of Navarra