ABSTRACT
The Sun provides nearly all of the energy that drives the Earth’s climate system. Although understanding the effects of solar variability on Earth’s climatic change remains one of the most puzzling questions that have continued to attract attention of scientists. The Sun has been observed to vary on all time-scales and there is increasing evidence that this variation may have an effect on the Earth’s climate. Scientists have been attempting to establish on the quantity of solar energy that illuminates the Earth and what occurs to the energy once it gets through the atmosphere. The climate response to these variations can be on a global scale but understanding the regional climate effects is more difficult. In this project research, we study the correlation between solar variability and the Earth’s climatic changes over the last 17 years. We make use of solar data from Solar Radiation and Climate Experiments (SORCE) and climate data from Climate Research Unit (CRU). In order to observe how these changes have occurred, analysis of the data was done using GNU-plot and python to show the trend. As an outcome, from the results we explore for the possible correlation linking the solar variability and the Earth’s climate change over the 17 years period. Our results show a linkage in the change of the climate factors which can be attributed to, but not completely to the solar variability. Further advances in understanding of the solar variability and its effect on climate are recommended from the ongoing acquisition of high-quality measurements of climate and solar variables. This knowledge is of importance as it can be used to in estimating the past and the future of solar behavior and climatic response.
TABLE OF CONTENTS
DECLARATION i
DEDICATION ii
ACKNOWLEDGEMENTS iii
ABSTRACT iv
TABLE OF CONTENTS v
LIST OF FIGURES viii
LIST OF ABBREVIATIONS/ ACRONYMS AND SYMBOLS ix
CHAPTER ONE
INTRODUCTION
1.1 Background information 1
1.2 Problem statement 4
1.3 Research Objectives 5
1.3.1 Main objective 5
1.3.2 Specific objectives 5
1.4 Justification and significance 5
CHAPTER TWO
LITERATURE REVIEW
CHAPTER THREE
THEORETICAL BACKGROUND
3.1 The Sun as a blackbody 11
3.2 Solar Luminosity 12
3.3 Effective temperature 13
3.4 Radiative forcing 15
3.5 Atmospheric gas forcing 16
3.6 Role of the middle atmosphere 16
3.7 Effect of energetic particle precipitation (EPP) on the atmosphere 17
3.8 Bottom-up and Top-down mechanisms 18
CHAPTER 4
METHODOLOGY
4.1 Introduction 19
4.2 Source of data 19
4.3 Data acquisition and analysis 20
4.4 Data smoothing 20
4.5 Linear regression 21
CHAPTER FIVE
RESULTS AND DISCUSSIONS
5.1 Introduction 22
5.2 Solar variability results 22
5.2.1 Total Solar Irradiance (TSI) 22
5.2.2 Solar Effective Temperature 24
5.2.3 Computed Solar Luminosity 25
5.2.4 Sunspot Numbers 27
5.2.5 Spectral Solar Irradiance (SSI) 29
5.3 Climate variability results 29
5.3.1 Carbon dioxide concentration 29
5.3.2 Global temperature anomalies 31
5.3.3 Global temperature anomalies of the northern hemisphere 34
5.3.3 Global temperature anomalies of the southern hemisphere 35
5.3.4 Global temperature anomalies of both hemispheres 35
5.4 Solar variability and climate change 36
5.4.1 TSI and Sunspot numbers 36
5.4.2 Global temperature anomaly and carbon dioxide concentration 37
5.4.3 Temperature anomalies and TSI 39
CHAPTER SIX
CONCLUSIONS AND RECOMMENDATIONS
6.1 Conclusions 40
6.2 Recommendations 40
REFERENCES 41
LIST OF FIGURES
Figure 1: Structure of the Sun (Source: The Sun Today- solar facts and space weather) 2
Figure 2: Spectral Irradiance of the Sun against wavelength (Source: Science Direct) 12
Figure 3: A graph of total solar irradiance over the 17 years 22
Figure 4: A graph of total solar irradiance over the 17 years fitted with polynomials. 23
Figure 5: A graph of computed effective temperature at 1AU 24
Figure 6: A graph of computed effective temperature at 1AU fitted with polynomial. 25
Figure 7: A graph of computed solar luminosity at 1 AU 26
Figure 8: A graph of computed effective temperature at 1AU fitted with polynomial. 27
Figure 9: A graph of sunspots numbers over the 17 years. 28
Figure 10: A graph of Spectral Solar Irradiance against the wavelength range 29
Figure 11: A graph of carbon dioxide concentration for the years 2003-2017 30
Figure 12: A graph of carbon dioxide concentration for the years 2003-2017 fitted with linear fit.. 31
Figure 13: A graph of global temperature anomalies over the 17 years. 32
Figure 14: A graph of global temperature anomalies with linear fit 33
Figure 15: A graph of global temperature anomalies of the northern hemisphere for the 17 years with linear fit 34
Figure 16: A graph of global temperature anomalies of the southern hemisphere for the 17 years. 35
Figure 17: A graph of global temperature anomalies of both hemispheres for the 17 years. 36
Figure 18: A graph showing the comparison TSI and Sunspot number 37
Figure 19: A graph of global temperature anomalies against carbon dioxide concentration. 38
Figure 20: A graph of global temperature anomalies and the TSI 39
LIST OF ABBREVIATIONS/ ACRONYMS AND SYMBOLS
TSI – Total Solar Irradiance SSI – Spectral Solar Irradiance SEP – Solar Energetic Particle
SIM – Spectral Irradiance Monitor
SOLSTICE – Solar Stellar Intercomparison Experiment SORCE – Solar Radiation and Climate Experiment CME – Coronal Mass Ejections
UV – Ultraviolet
HEP – High Energy Particle GSM – Grand Solar Minimum SEP – Solar Energetic Particles GCR – Galactic Cosmic Rays
CHAPTER ONE
INTRODUCTION
1.1 Background information
We live on a planet, Earth, which is part of the solar system that is Sun centered. The Sun is the main originator of energy that sustains life on Earth. It is almost an ideal sphere of hot plasma heated to blaze as a result of the nuclear fusion reactions taking place at the core hence radiating energy as infrared radiation and visible light. The Sun is known to have formed through self-gravitational collapse of a cloud of dust and gas. Majority of this matter collected in the middle via self- gravitating, as the rest flattened into an orbiting disk that formed the solar system.
The Sun has a diameter of approximately 1.39 million kilometers, or its diameter is 109 times that of the Earth, it has a mass that accounts for around 99.86% that of the solar system and it is around 330,000 times that of the Earth. It has a composition of approximately 70% hydrogen, 28% helium and other smaller quantities of heavier elements which include carbon, oxygen, iron and neon. The Sun’s age is approximately 4.6 billion years and has a luminosity of 3.828×1026 Watts. It rotates about once every 27 days on average, with the poles rotating every 24 days and the equator every 30 days.
The Sun’s structure comprises of the following layers: 1) The core, which is the innermost layer occupying between 20 to 25% of the Sun’s radius, where temperatures (approximately 15 million Kelvin) and pressure (approximately 26.5 petapascals) are sufficiently high for nuclear fusion to occur. The nuclear fusion produces energy that makes the core becomes rich in helium. 2) The radiative zone, this is the layer just after the Sun’s core. Energy transfer in this layer occurs by means of radiation. 3) Tachocline, which is the region that creates the boundary linking the radiative zone and the convective zone. 4) Convective zone, which is the layer between the Radiative zone and a close point to the visible Sun’s surface. In this layer, the temperatures are cool such that convection can take place and this forming the fundamental method of extrinsic heat transfer. 5) The photosphere, this is the deepest section of the Sun, and can be directly observed. The Sun is made up of gas and it lacks a distinctly defined surface. The visible part is categorised into the photosphere and the atmosphere. The atmosphere is a gaseous ring of light surrounding the Sun and is made up of four parts, which are the transition region, chromosphere, the heliosphere and the corona. This layer is most visible during a solar eclipse. Figure 1 shows the structure of the Sun.
