Population effects of increase in world energy use and CO2 emissions: 1990–2019

![Figure][1] The theme for the 2007 annual meeting of the AAAS, to be held in San Francisco on 15 to 19 February, is “Science and Technology for Sustainable Well-Being.” The problem of energy, which is the focus of this special issue of Science linked to the meeting, looms as a central element in the web of intertwined challenges that this theme embodies. Well-being has environmental, sociopolitical, and cultural dimensions as well as economic ones, and the goal of sustainable well-being entails improving all of these dimensions in ways and to end points that are consistent with maintaining the improvements indefinitely. This challenge includes not only improving sustainably the standard of living in developing countries, but also converting to a sustainable basis the currently unsustainable practices supporting the standard of living in industrialized ones. Civilization's ability to meet this immense challenge clearly depends on our strengths in natural science and engineering. But it also depends on our strengths in the social sciences and in “social technology” in the form of business, government, and law, as well as on the societal wit and will to integrate all of these elements in pursuit of the sustainable-well-being goal. ![Figure][1] CREDIT: JUPITER IMAGES No part of this challenge is more complex or more demanding than its energy dimension. This is so in part because energy supply is tightly intertwined with national and international security and with many of the most damaging and dangerous environmental problems—from indoor air quality to global climate change—as well as with the capacity to meet basic human needs and fuel economic growth. The multiplicity and importance of these linkages would make energy a vexing issue even in a world where energy demand was constant. But that is not the world we live in. Continuing population growth and rapidly rising affluence in many parts of the globe are driving a rate of increase in energy use that has staggering implications. Even if the energy efficiency of the world economy—gross world product per unit of energy—were to continue to increase at the long-term historical rate of about 1% per year, the realization of middle-of-the-road population and economic projections would entail quadrupling world energy use in this century. In a world where today one-third of primary energy comes from oil (two-thirds of the remaining high-quality supplies of which probably lie under the volatile Middle East) and 80% comes from oil, coal, and natural gas combined (virtually all of the carbon dioxide from the combustion of which continues to go straight into the atmosphere), that middle-of-the-road energy trajectory cannot be managed simply by expanding what we are already doing. Such a path is not merely unsustainable; it is a prescription for disaster. The perils of oil dependence and climate change, coupled with the demand for large increases in the per-capita availability of energy services, compel an early transition to a different path. Its requirements include a reduction in global population growth (achievable, fortunately, by means that are desirable in their own right) and a sharply increased emphasis on improving the efficiency of energy conversion and end use (aiming to improve the energy efficiency of the world economy not by 1% per year but by 2% per year or more). Also required is a several fold increase in public and private investments to improve the technologies of energy supply. We need to know whether and how the carbon dioxide from fossil-fuel use can be affordably and reliably sequestered away from the atmosphere; whether and how nuclear energy can be made safe enough and proliferation-resistant enough to be substantially expanded worldwide; and to what extent biofuel production can be increased without intolerable impacts on food supply or ecosystem services. And we need to improve the affordability of the direct harnessing of sunlight for society's energy needs. Much insight about the current prospects in these and other dimensions of the energy problem is available in this special issue of Science. Still more about energy is on the agenda for the San Francisco meeting, along with much else germane to “Science and Technology for Sustainable Well-Being.” I commend it all to your attention. Nothing is more important to the human condition in the 21st century than rising to this set of challenges. [1]: pending:yes

Roughly half of the world’s population lives in urban areas, and this share is increasing over time, projected to reach 60% by 2030. Cities consume a great majority – between 60 to 80% – of energy production worldwide and account for a roughly equivalent share of global CO2 emissions. Greenhouse gas (GHG) emissions in OECD cities are increasingly driven less by industrial activities and more by the energy services required for lighting, heating and cooling, electronics use, and transport mobility. Cities can in principle use energy in a more efficient way than more dispersed areas because of reduced costs and economies of scale, however this depends on urban design and form. Growing urbanisation will lead to a significant increase in energy use and CO2 emissions, particularly in non-OECD countries in Asia and Africa where urban energy use is shifting from CO2-neutral energy sources such as biomass and waste to CO2-intensive energy sources.

Energy-related data for China, India, the United States, and the world were analyzed for the period 2005–2035 to gain insight on (1) the evolution of energy intensity, (2) the pattern of carbon-dioxide equivalent (CO 2 ) emitted per unit of GDP, (3) reductions in the carbon intensity required to achieve CO 2 emissions comparable to the 1990 Kyoto Protocol's baseline year, (4) key obstacles to transitioning to a world's economy less dependent on fossil fuels. Key findings are: (1) the world's total primary energy use is expected to increase by 56% in the period 2005–2035, (2) the world's rate of GDP growth outpaces its rate of increase in energy use because of a decrease in the energy/GDP ratio, (3) the world's carbon intensity in 2035 must undergo a near 4-fold reduction to achieve emissions equal to those of 1990, (4) there are major obstacles to transitioning to a world much less reliant on fossil fuels.

As artificial intelligence (AI) becomes more integrated into society, concerns have arisen about unintended biases in AI-driven decision-making and the environmental impact of AI technology development. AI assistants such as Siri and Alexa, while helpful, can obscure decision-making and contribute to increased energy use and CO2 emissions. The present study explores whether consumers prioritize transparency and environmental sustainability over performance when choosing AI assistants with conjoint designs. Japanese participants were presented with different AI assistant profiles, varying in performance quality, transparency, cost, and environmental efficiency. The results revealed that Japanese participants prioritized transparency over performance when choosing AI assistants, but they prioritized performance over environmental sustainability. Moreover, future-oriented participants placed more importance on sustainability than those with a present orientation, while participants with an internal locus of control valued transparency more than those with an external locus of control. The findings of this study enhance our understanding of how consumers choose AI options and offer valuable guidance for creating AI systems and communication strategies that work effectively.

This paper empirically investigates the effect of energy use on economic growth throughout different stages of development. Along with direct effects, energy is allowed to influence income growth indirectly by capital accumulation through input substitution. We find that energy use affects economic growth primarily through the capital channel and that this result varies substantially with regard to the country's income level. For middle-income countries including the quintet of large emerging economies – Brazil, Russia, India, China and South Africa – an increase in energy use drives capital accumulation, which favors economic growth. On the contrary, for high-income countries, a higher energy input tends to withdraw productive resources from capital accumulation, harming economic growth. Considering these differences, policy measures aiming at restricting energy consumption should be evaluated against the background of a region's stage of economic development.

Effect of winter feeding systems on farm greenhouse gas emissions

The energy use and emissions from direct fossil fuel combustion on-farms to power farm machinery was critically reviewed. Approximately, 15% of agricultural production costs on-farm are energy-related. A potential solution to more sustainable energy use is a shift toward biofuels from renewable resources. The reduction of greenhouse gas emissions through the substitution of diesel oil with biodiesel depends on the feedstock, the inter-esterification process, the storage period, and ambient conditions. In modern tractors, increased fuel use efficiency (or reduced fuel consumption) has been achieved by power/load matching and the use of variable transmission. Engine management systems that are capable of continuously communicating with the engine and transmission to make appropriate adjustments based on inputs received from the tractor allow for quick and precise responses to changing conditions. As a result, maximum efficiency and productivity can be obtained from the tractor operating similarly to the traditional ‘gear-up and throttle-back’ methods of a proficient operator. The future for autonomous tractors is promising, though not new. Electric-powered tractors are near to commercialization or are already commercially available. Hybrid electric driven tractors present some advantages in terms of increased energy use efficiency and functionalities. Increased efficiency can lead to a reduction in diesel fuel consumption and hence, a concurrent decrease in CO2 emission. Where the local electricity supply has a low-carbon emission factor, this can also result in significant emission reductions. Small light-weight robotic equipment can potentially perform functions currently undertaken by tractor-drawn and other heavy equipment with high-fuel consumption, provided field operating capacity was not compromised. However, the size and weight limitations inherent in current harvesting and transport technology mean that soil compaction will still be a problem with robotic units. The robotic operation of medium-scale equipment within a precision-controlled traffic farming environment should offer more feasible and energy-efficient alternatives.

Today’s websites include multimedia and interactive features that increase energy use and CO2 emissions. Although front-end optimization techniques are common, their actual environmental impact has been underexplored. This study examined the effects of image compression, lazy loading, and code minification—individually and in combination—on client-side energy consumption and emissions. A controlled laboratory experiment was conducted with eight variants of the website, including a baseline and combinations of the three techniques. Energy use was measured with Firefox Energy Profiler for CPU and graphics processing components and with a Tuya smart plug for whole-device consumption. Automated browsing ensured consistent interactions across trials. The findings show that image compression provided the strongest single benefit, reducing system-level energy by 47.5%. The combinations achieved far greater effects, with image compression plus code minification cutting the energy of the entire device by 89.8% and CO2 emissions by 89.6%. The results demonstrate that standard front-end optimizations, when applied together, substantially lower the environmental footprint of web applications.

Energy demand is expected to grow rapidly in the next decades, with world energy use rising by 57% by 2030, compared with 2004 levels, according to a new report from the U.S. Energy Information Administration. Much of this growth is expected outside of developed countries within the Organization for Economic Cooperation and Development; these non‐OECD countries will account for about 95% of the projected growth. Although rising oil prices are expected to dampen growth in this sector, their consumption is expected to reach 118 million barrels per day in 2030, 35 million barrels per day more than in 2004. Overall nuclear energy capacity will rise from 368 gigawatts in 2004 to 481 gigawatts in 2030, but declines are projected in several European countries that are planning to phase out the use of nuclear power.

In recent years, demand for energy has surged. This unrelenting increase has helped fuel global economic growth but placed considerable pressure on suppliers buffeted by geopolitics, violent weather conditions and other potentially disruptive factors. On the demand side, increased energy security and environmental concerns may lead to changes in consuming countries’ energy policies. These uncertainties have been reflected in the market through volatility and high prices. Is the world running out of energy? Where will future supplies come from? Will adequate investment be made to make available adequate energy supplies to meet future demand? What role will governments play? The oil and gas resources of the Middle East and North Africa (MENA) will be critical to meeting the world’s growing appetite for energy. A large share of the world’s remaining reserves lie in that region. They are relatively under-exploited and so there is considerable potential for increasing production. But there is considerable uncertainty about the pace at which investment in the region’s upstream industry will actually occur, how quickly production capacity will expand and, given rising domestic energy needs, how much of the expected increase in supply will be available for export. The implications for both MENA producers and consuming countries are profound. This paper draws on the main findings of the World Energy Outlook 2005, published by the International Energy Agency. The 2005 Outlook assesses quantitatively the prospects for global energy markets through to 2030, with a special focus on the Middle East and North Africa. In addition, it analyses the possible impact of deferred investment in the region’s energy sector and also considers the potential effects of changing policies in consumer countries to address energy security and environmental concerns. The World Energy Outlook 2006 will build on this analysis and develop it even further. Global Energy Trends Global energy needs are likely to continue to grow steadily for at least the next two-and-ahalf decades. If governments stick with current policies – the underlying premise of the World Energy Outlook’s Reference Scenario – the world’s energy needs would be more than 50% higher in 2030 than today, an average annual growth rate of 1.6%. More than twothirds of the growth in world energy use will come from the developing countries, where economic and population growth are highest.

The economic complexity index's environmental implications have been thoroughly investigated in this study. In particular, an effort is made to determine the index's utility in explaining and filling in the gaps left by experimental studies on the effects of renewable energy on CO2 emissions. The study sampled 29 Asia-Pacific countries over the period 2000–2018. The relationship between the complexity index and CO2 emissions has been investigated using panel data models and estimation methods. According to the findings, increasing the intensity of energy use, trade openness, and urbanization all increase CO2 emissions, although the effects of urbanization eventually became insignificant in the long run. Furthermore, while the logarithm of GDP per capita’s coefficients for the level and squared forms confirmed the Environmental Kuznets Curve (EKC) hypothesis, the economic complexity index shifted the curve. The results indicate that economic complexity in countries enhances economic growth effects to increase CO2 emissions through increased production scale and energy demand. On the other hand, increasing economic complexity through increased energy efficiency demonstrates its beneficial effects on the environment. According to the findings, increasing wind and solar energy share has reduced CO2 emissions in countries with lower economic complexity. In comparison, in more complex countries along with these substitution effects, there is also a scale effect associated with increasing renewable energy use, which eventually results in increased CO2 emissions.

<p class="MsoNormal" style="margin-top: 10pt; text-align: justify;"><span lang="EN-US" style="font-family: 'times new roman', times, serif; font-size: 14pt;">This study employs empirical analysis using an econometric model that examines the interdependence among environmental degradation, exports, and economic development with energy use. It also provides an environmental Kuznets curve (EKC) for selected South Asian economies utilizing time-series data. The findings reveal a long-term, stable equilibrium link between energy demand and pollution. There exists a positive relationship between structural factors and pollution. Moreover, this study constructs a model of exports and pollution from an interdependent perspective. The three perspectives are tested: the scale and structure of energy consumption considering the twin constraints of export-trade and pollution, and the scale of pollution in export-trade constraint. These results show that the increase in energy use leads to higher CO2 emissions amidst export volume. However, in the presence of income, the scale of effect lowers a little. The analysis also supports the presence of Kuznets curve for south-Asian economies. The results imply substantial scope for development in the energy use and pollution structure within South Asia's current export trade process. This development can be attained by regulating energy use and enhancing system efficacy without necessitating changes to the scale effect or structural effect.</span></p>

Hydrophobic- and fat-dissolved rice straw-C induced equivalent amount of CO2 emission and soil net C balance

Transport is an essential infrastructure for development. With its high share of gross domestic product (GDP), it makes a significant contribution to total CO2 emissions in Malaysia. It is therefore important to pay greater attention to reducing CO2 emissions and sustainable development in this sector. Therefore, this study aims at estimating the relationship between transport CO2 emissions and its key drivers using the Autoregressive Distributed Lag (ARDL) technique. The time period covered by the study extends from 1978 to 2018. It further investigates the response of CO2 emissions to shocks in the value of other variables by employing the generalized impulse response approach. The results suggest that urbanization is the major contributor to the increase in CO2 emissions followed by the carbon intensity of energy in the long-run. Carbon intensity of energy, GDP per transport worker and urbanization contribute significantly to increases in transport CO2 emissions in the short- and long-run. Testing the Environmental Kuznets Curve (EKC) hypothesis recommends that Malaysia continue to be on track to reach the highest level of income and welfare to give pay more attention to the environment. Therefore, the country maintains its CO2 emissions level in the future because of economic development. Therefore, these findings show that energy and environmental policymakers need to pay more attention to improving energy efficiency and the use of low-carbon technologies and electrification in the transport sector and the use of high-quality public transport, particularly in urban areas, for sustainable urban development.

Natural resource abundance, growth-oriented strategies and low environmental concern of post-Soviet states may exacerbate the consequences of climate change significantly. This study considers the relationship between CO2 emissions, economic development, foreign investment inflows, trade and energy use in 20 post-Soviet states between 1995 and 2017. A panel cointegration test reveals the long-term cointegrating relationship between the variables. Long-term elasticities are reported using Dynamic Ordinary Least Squares and Fully Modified Ordinary Least Squares regressions, which yield quite similar results: GDP per capita, foreign direct investment (FDI) inflows, trade and energy use positively related to CO2 emissions per capita in the long term. A panel causality test, however, identifies unidirectional causality running from CO2 emissions to energy use at p<0.01. In other words, greater economic activity in terms of foreign capital inflows, larger trade shares, extensive energy use and economic development, harm the environment through increasing CO2 emissions and strengthen the need for greater environmental and climate change concerns. The study aims to contribute to this Special Issue through accounting for the role of foreign direct investment and foreign trade in the sustainable development of post-Soviet states.